<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:6ee85aef-9dce-4430-bbde-7bf5ccae42c2,g:6f87242f-e5ae-497c-ba55-187af8e86fe4-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.omnicell.com/role/CondensedConsolidatedStatementsofOperationsUnaudited" xlink:type="simple" xlink:href="omcl-20240630.xsd#CondensedConsolidatedStatementsofOperationsUnaudited"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/CondensedConsolidatedStatementsofOperationsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_0a879bd4-0176-49c7-a3f0-b0a846d01d38" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_StatementTable_0a879bd4-0176-49c7-a3f0-b0a846d01d38" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_584f56d7-ff33-4b62-837d-e343ec5d127b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_0a879bd4-0176-49c7-a3f0-b0a846d01d38" xlink:to="loc_srt_ProductOrServiceAxis_584f56d7-ff33-4b62-837d-e343ec5d127b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_584f56d7-ff33-4b62-837d-e343ec5d127b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_584f56d7-ff33-4b62-837d-e343ec5d127b" xlink:to="loc_srt_ProductsAndServicesDomain_584f56d7-ff33-4b62-837d-e343ec5d127b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_fd40f286-cd5c-4af0-b8ef-a83ba64d8a5a" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_584f56d7-ff33-4b62-837d-e343ec5d127b" xlink:to="loc_srt_ProductsAndServicesDomain_fd40f286-cd5c-4af0-b8ef-a83ba64d8a5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_1456e296-2e60-43c2-8447-673c98452cf0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_fd40f286-cd5c-4af0-b8ef-a83ba64d8a5a" xlink:to="loc_us-gaap_ProductMember_1456e296-2e60-43c2-8447-673c98452cf0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_e606cec3-83c2-4467-a8ff-9fecc80f6a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_fd40f286-cd5c-4af0-b8ef-a83ba64d8a5a" xlink:to="loc_us-gaap_ServiceMember_e606cec3-83c2-4467-a8ff-9fecc80f6a7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_6690adb4-3203-49ca-99ed-3657cca6c221" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_6690adb4-3203-49ca-99ed-3657cca6c221" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_6bd3535d-8847-4e21-8bc3-7e860eb03589" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_6bd3535d-8847-4e21-8bc3-7e860eb03589" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_98b6d47c-9d32-4fe1-983c-6b5168601e74" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_GrossProfit_98b6d47c-9d32-4fe1-983c-6b5168601e74" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_daa67c91-9cbb-4d9b-b8c5-319d9e938935" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_OperatingExpensesAbstract_daa67c91-9cbb-4d9b-b8c5-319d9e938935" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_17316a27-703f-4d25-be3b-c131b2a778c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_daa67c91-9cbb-4d9b-b8c5-319d9e938935" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_17316a27-703f-4d25-be3b-c131b2a778c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_7bdcf5fe-50be-4766-81c7-fd9de1ca3b40" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_daa67c91-9cbb-4d9b-b8c5-319d9e938935" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_7bdcf5fe-50be-4766-81c7-fd9de1ca3b40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_4a9323ac-885c-4f09-86c9-e230bd898207" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_daa67c91-9cbb-4d9b-b8c5-319d9e938935" xlink:to="loc_us-gaap_OperatingExpenses_4a9323ac-885c-4f09-86c9-e230bd898207" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_a085a589-a421-41bc-97cc-7667dbd85d8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_OperatingIncomeLoss_a085a589-a421-41bc-97cc-7667dbd85d8c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_26fba126-4ccb-41d7-bdc0-745ba20b1f8d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_26fba126-4ccb-41d7-bdc0-745ba20b1f8d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_9ba81bbd-bb5e-48c6-9aef-0931dbbd43a4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_9ba81bbd-bb5e-48c6-9aef-0931dbbd43a4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_38fce829-bc6b-483d-a9a1-d5ea71e8752b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_38fce829-bc6b-483d-a9a1-d5ea71e8752b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_6dc76d77-691b-47e2-ade2-3c2456325091" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_NetIncomeLoss_6dc76d77-691b-47e2-ade2-3c2456325091" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareReconciliationAbstract_ffee07f9-1994-4ed3-8dcb-6fced779fb54" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareReconciliationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_EarningsPerShareReconciliationAbstract_ffee07f9-1994-4ed3-8dcb-6fced779fb54" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_89a6ec60-fd05-4382-b5bf-e9fe23197d9f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_ffee07f9-1994-4ed3-8dcb-6fced779fb54" xlink:to="loc_us-gaap_EarningsPerShareBasic_89a6ec60-fd05-4382-b5bf-e9fe23197d9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_deda723c-9303-455d-8943-699d80ad9ede" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_ffee07f9-1994-4ed3-8dcb-6fced779fb54" xlink:to="loc_us-gaap_EarningsPerShareDiluted_deda723c-9303-455d-8943-699d80ad9ede" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_e273561d-bd0b-4722-9f71-35c94bc3b83a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca7752b6-da94-4569-a82d-359837c27676" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_e273561d-bd0b-4722-9f71-35c94bc3b83a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_cee14a2a-2da7-4ac1-bfca-04e60340c89f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_e273561d-bd0b-4722-9f71-35c94bc3b83a" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_cee14a2a-2da7-4ac1-bfca-04e60340c89f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_57494fa2-838f-4fad-a7b5-eff8217167fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_e273561d-bd0b-4722-9f71-35c94bc3b83a" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_57494fa2-838f-4fad-a7b5-eff8217167fe" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/CondensedConsolidatedStatementsofStockholdersEquityUnaudited" xlink:type="simple" xlink:href="omcl-20240630.xsd#CondensedConsolidatedStatementsofStockholdersEquityUnaudited"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/CondensedConsolidatedStatementsofStockholdersEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e9f16849-b65f-48fe-8175-b9e6b9404b4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6fd328a3-2ba5-4611-9e9e-9d0d70d15f72" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_e9f16849-b65f-48fe-8175-b9e6b9404b4c" xlink:to="loc_us-gaap_StatementTable_6fd328a3-2ba5-4611-9e9e-9d0d70d15f72" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_4a8b6eaf-7ce2-4ae3-90d4-03fb3e395df9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6fd328a3-2ba5-4611-9e9e-9d0d70d15f72" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_4a8b6eaf-7ce2-4ae3-90d4-03fb3e395df9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_4a8b6eaf-7ce2-4ae3-90d4-03fb3e395df9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4a8b6eaf-7ce2-4ae3-90d4-03fb3e395df9" xlink:to="loc_us-gaap_EquityComponentDomain_4a8b6eaf-7ce2-4ae3-90d4-03fb3e395df9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_0aeea07f-de25-4471-929d-6dc87be3c340" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4a8b6eaf-7ce2-4ae3-90d4-03fb3e395df9" xlink:to="loc_us-gaap_EquityComponentDomain_0aeea07f-de25-4471-929d-6dc87be3c340" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_88c0b109-9be9-4b0f-8cf0-75bc0f6cd39a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0aeea07f-de25-4471-929d-6dc87be3c340" xlink:to="loc_us-gaap_CommonStockMember_88c0b109-9be9-4b0f-8cf0-75bc0f6cd39a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_379b2939-abf9-4014-ab23-783bb03afe9c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0aeea07f-de25-4471-929d-6dc87be3c340" xlink:to="loc_us-gaap_TreasuryStockCommonMember_379b2939-abf9-4014-ab23-783bb03afe9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_f8452005-0e2d-4382-a34e-404a7a490cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0aeea07f-de25-4471-929d-6dc87be3c340" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_f8452005-0e2d-4382-a34e-404a7a490cbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_ea61da3a-01e0-48cd-8403-b05dbb3bf7f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0aeea07f-de25-4471-929d-6dc87be3c340" xlink:to="loc_us-gaap_RetainedEarningsMember_ea61da3a-01e0-48cd-8403-b05dbb3bf7f4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_43b70bfa-144f-4ff5-aa87-bfabb27e6175" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0aeea07f-de25-4471-929d-6dc87be3c340" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_43b70bfa-144f-4ff5-aa87-bfabb27e6175" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9f16849-b65f-48fe-8175-b9e6b9404b4c" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_9593e512-5713-4e62-91ce-eaa2d8070b56" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_9593e512-5713-4e62-91ce-eaa2d8070b56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_8167c55c-5f76-4ab5-8f1d-761fc37dffb7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_StockholdersEquity_8167c55c-5f76-4ab5-8f1d-761fc37dffb7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_097e1a17-c3aa-46d9-aa41-6586f24006b2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_TreasuryStockCommonShares_097e1a17-c3aa-46d9-aa41-6586f24006b2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_292d557b-2c35-4497-9701-ab39e72bc1e7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_NetIncomeLoss_292d557b-2c35-4497-9701-ab39e72bc1e7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_2f835af9-4c1c-4f9a-9933-1fe7c254dde7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_2f835af9-4c1c-4f9a-9933-1fe7c254dde7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_18f844dc-a334-4f15-8fb7-09286a377dda" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_18f844dc-a334-4f15-8fb7-09286a377dda" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_3ac6e57e-f753-4fe2-9def-c3be4d7f486f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_3ac6e57e-f753-4fe2-9def-c3be4d7f486f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_ccd85d16-a5e6-43ac-ba6e-192cb9fbe5fd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_ccd85d16-a5e6-43ac-ba6e-192cb9fbe5fd" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_bf2be88c-4251-446c-833e-5cc66e103d33" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_92c2a896-053d-49fe-a96a-b58fa0f75058" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_bf2be88c-4251-446c-833e-5cc66e103d33" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_c10f74ba-d3e1-4b3e-934c-a1a5b4c60596" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_2dd838ec-64aa-4034-bbf5-ce738e0a839c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_2d9e7715-d399-464a-a1f7-5d5cf494f97d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/RevenuesNarrativeDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#RevenuesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/RevenuesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_5cc0342a-61b6-482e-bef2-3f3827109e4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_5cc0342a-61b6-482e-bef2-3f3827109e4c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_419bcbb2-e623-41d4-99e5-cb7c6a056ddf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_5cc0342a-61b6-482e-bef2-3f3827109e4c" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_419bcbb2-e623-41d4-99e5-cb7c6a056ddf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_GroupPurchasingOrganizationFees_beb5e14c-943f-4bee-afd3-bc8f5bd6f662" xlink:href="omcl-20240630.xsd#omcl_GroupPurchasingOrganizationFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_GroupPurchasingOrganizationFees_beb5e14c-943f-4bee-afd3-bc8f5bd6f662" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_b4520a3f-53db-447f-8cf5-3307554ce9ef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_b4520a3f-53db-447f-8cf5-3307554ce9ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ContractWithCustomerAssetCurrentDeferredCostOfGoodsAndServicesSold_db32e7cc-faf6-492f-9fd9-7896978322b2" xlink:href="omcl-20240630.xsd#omcl_ContractWithCustomerAssetCurrentDeferredCostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_ContractWithCustomerAssetCurrentDeferredCostOfGoodsAndServicesSold_db32e7cc-faf6-492f-9fd9-7896978322b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_11be0fb3-12ca-4f6c-b371-38a9d3fc7282" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_11be0fb3-12ca-4f6c-b371-38a9d3fc7282" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ContractWithCustomerLiabilityCurrentGross_99eecafb-9ce8-46b7-831c-3fab577aad5b" xlink:href="omcl-20240630.xsd#omcl_ContractWithCustomerLiabilityCurrentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_ContractWithCustomerLiabilityCurrentGross_99eecafb-9ce8-46b7-831c-3fab577aad5b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_RevenueFromContractWithCustomerMaximumContractTerm_ec012f68-1b64-4202-a4e9-2de26252f2e6" xlink:href="omcl-20240630.xsd#omcl_RevenueFromContractWithCustomerMaximumContractTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_RevenueFromContractWithCustomerMaximumContractTerm_ec012f68-1b64-4202-a4e9-2de26252f2e6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_7b2952c8-993e-419e-a323-f630b867a3e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_7b2952c8-993e-419e-a323-f630b867a3e9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1e7526ea-5191-44b9-85a2-141b283c0db9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1e7526ea-5191-44b9-85a2-141b283c0db9" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/RevenuesNarrativeDetails_1" xlink:type="simple" xlink:href="omcl-20240630.xsd#RevenuesNarrativeDetails_1"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/RevenuesNarrativeDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_5cc0342a-61b6-482e-bef2-3f3827109e4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_5cc0342a-61b6-482e-bef2-3f3827109e4c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_GroupPurchasingOrganizationFees_beb5e14c-943f-4bee-afd3-bc8f5bd6f662" xlink:href="omcl-20240630.xsd#omcl_GroupPurchasingOrganizationFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_GroupPurchasingOrganizationFees_beb5e14c-943f-4bee-afd3-bc8f5bd6f662" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_b4520a3f-53db-447f-8cf5-3307554ce9ef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_b4520a3f-53db-447f-8cf5-3307554ce9ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ContractWithCustomerAssetCurrentDeferredCostOfGoodsAndServicesSold_db32e7cc-faf6-492f-9fd9-7896978322b2" xlink:href="omcl-20240630.xsd#omcl_ContractWithCustomerAssetCurrentDeferredCostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_ContractWithCustomerAssetCurrentDeferredCostOfGoodsAndServicesSold_db32e7cc-faf6-492f-9fd9-7896978322b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_11be0fb3-12ca-4f6c-b371-38a9d3fc7282" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_11be0fb3-12ca-4f6c-b371-38a9d3fc7282" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ContractWithCustomerLiabilityCurrentGross_99eecafb-9ce8-46b7-831c-3fab577aad5b" xlink:href="omcl-20240630.xsd#omcl_ContractWithCustomerLiabilityCurrentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_ContractWithCustomerLiabilityCurrentGross_99eecafb-9ce8-46b7-831c-3fab577aad5b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_RevenueFromContractWithCustomerMaximumContractTerm_ec012f68-1b64-4202-a4e9-2de26252f2e6" xlink:href="omcl-20240630.xsd#omcl_RevenueFromContractWithCustomerMaximumContractTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_omcl_RevenueFromContractWithCustomerMaximumContractTerm_ec012f68-1b64-4202-a4e9-2de26252f2e6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_7b2952c8-993e-419e-a323-f630b867a3e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_7b2952c8-993e-419e-a323-f630b867a3e9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1e7526ea-5191-44b9-85a2-141b283c0db9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_28028c7d-f9a4-4ad6-8d14-f08484cf810f" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1e7526ea-5191-44b9-85a2-141b283c0db9" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/RevenuesDisaggregationofRevenuesbyRevenueTypeDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#RevenuesDisaggregationofRevenuesbyRevenueTypeDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/RevenuesDisaggregationofRevenuesbyRevenueTypeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_e1145dad-513a-42c0-9def-3f13eb1953ee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_5b1816f1-705d-4496-9a2d-0c1cece02d5e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_e1145dad-513a-42c0-9def-3f13eb1953ee" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_5b1816f1-705d-4496-9a2d-0c1cece02d5e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_153dc091-d724-4bd7-bcad-671e5fb9188b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_5b1816f1-705d-4496-9a2d-0c1cece02d5e" xlink:to="loc_srt_ProductOrServiceAxis_153dc091-d724-4bd7-bcad-671e5fb9188b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_153dc091-d724-4bd7-bcad-671e5fb9188b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_153dc091-d724-4bd7-bcad-671e5fb9188b" xlink:to="loc_srt_ProductsAndServicesDomain_153dc091-d724-4bd7-bcad-671e5fb9188b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_1be6d75b-6ddb-4d4d-abfc-251e2ef89f83" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_153dc091-d724-4bd7-bcad-671e5fb9188b" xlink:to="loc_srt_ProductsAndServicesDomain_1be6d75b-6ddb-4d4d-abfc-251e2ef89f83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConnectedDevicesSoftwareLicensesAndOtherMember_bae1bd56-5901-4619-bd55-2d97cebb3b13" xlink:href="omcl-20240630.xsd#omcl_ConnectedDevicesSoftwareLicensesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1be6d75b-6ddb-4d4d-abfc-251e2ef89f83" xlink:to="loc_omcl_ConnectedDevicesSoftwareLicensesAndOtherMember_bae1bd56-5901-4619-bd55-2d97cebb3b13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConsumablesMember_fd3bd7aa-02e4-4190-9cea-d2b28bc6f422" xlink:href="omcl-20240630.xsd#omcl_ConsumablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1be6d75b-6ddb-4d4d-abfc-251e2ef89f83" xlink:to="loc_omcl_ConsumablesMember_fd3bd7aa-02e4-4190-9cea-d2b28bc6f422" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_TechnicalServicesMember_1bf1ab10-8902-48f5-988d-3c4f89461463" xlink:href="omcl-20240630.xsd#omcl_TechnicalServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1be6d75b-6ddb-4d4d-abfc-251e2ef89f83" xlink:to="loc_omcl_TechnicalServicesMember_1bf1ab10-8902-48f5-988d-3c4f89461463" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_AdvancedServicesMember_364d8df5-8dc0-4285-a509-a3a50eb9be2e" xlink:href="omcl-20240630.xsd#omcl_AdvancedServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1be6d75b-6ddb-4d4d-abfc-251e2ef89f83" xlink:to="loc_omcl_AdvancedServicesMember_364d8df5-8dc0-4285-a509-a3a50eb9be2e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_070a3ef4-740b-46d0-af2d-bbe6aeedf71f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_e1145dad-513a-42c0-9def-3f13eb1953ee" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_070a3ef4-740b-46d0-af2d-bbe6aeedf71f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/RevenuesDisaggregationofRevenuesbyGeographicLocationDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#RevenuesDisaggregationofRevenuesbyGeographicLocationDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/RevenuesDisaggregationofRevenuesbyGeographicLocationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_6df86475-cd28-4b47-9418-218da9ef7728" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_43d12c40-0aa0-45b2-ba27-39a8c8b74e7e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_6df86475-cd28-4b47-9418-218da9ef7728" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_43d12c40-0aa0-45b2-ba27-39a8c8b74e7e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_d012c29c-c80f-4e2c-b7bf-7142a482608b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_43d12c40-0aa0-45b2-ba27-39a8c8b74e7e" xlink:to="loc_srt_StatementGeographicalAxis_d012c29c-c80f-4e2c-b7bf-7142a482608b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_d012c29c-c80f-4e2c-b7bf-7142a482608b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_d012c29c-c80f-4e2c-b7bf-7142a482608b" xlink:to="loc_srt_SegmentGeographicalDomain_d012c29c-c80f-4e2c-b7bf-7142a482608b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_cda91df4-3f0c-48ae-9dc8-f1f11a66a51b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_d012c29c-c80f-4e2c-b7bf-7142a482608b" xlink:to="loc_srt_SegmentGeographicalDomain_cda91df4-3f0c-48ae-9dc8-f1f11a66a51b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_ec8a6dd8-339e-4378-8096-011bd239f0e1" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cda91df4-3f0c-48ae-9dc8-f1f11a66a51b" xlink:to="loc_country_US_ec8a6dd8-339e-4378-8096-011bd239f0e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_b85234ef-ba74-40a4-9195-4380645087f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cda91df4-3f0c-48ae-9dc8-f1f11a66a51b" xlink:to="loc_us-gaap_NonUsMember_b85234ef-ba74-40a4-9195-4380645087f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a282ed35-ac92-43cd-886d-ed3072829a80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_6df86475-cd28-4b47-9418-218da9ef7728" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a282ed35-ac92-43cd-886d-ed3072829a80" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/NetIncomeLossPerShareDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#NetIncomeLossPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/NetIncomeLossPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_dfe57605-7afa-441b-9851-1e774b08dd25" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_dfe57605-7afa-441b-9851-1e774b08dd25" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_fa48ef70-363f-4f59-a91d-38600fc74c9a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_dfe57605-7afa-441b-9851-1e774b08dd25" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_fa48ef70-363f-4f59-a91d-38600fc74c9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_fa48ef70-363f-4f59-a91d-38600fc74c9a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_fa48ef70-363f-4f59-a91d-38600fc74c9a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_fa48ef70-363f-4f59-a91d-38600fc74c9a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c3a08949-a213-488a-a587-2a4b5d027ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_fa48ef70-363f-4f59-a91d-38600fc74c9a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c3a08949-a213-488a-a587-2a4b5d027ce2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_8f727359-e0c1-4ae1-85a4-1ca3ffab6813" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c3a08949-a213-488a-a587-2a4b5d027ce2" xlink:to="loc_us-gaap_StockCompensationPlanMember_8f727359-e0c1-4ae1-85a4-1ca3ffab6813" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConvertibleDebtSecuritiesAndWarrantsMember_80cf3b0d-db85-4895-99a9-58b445ebf941" xlink:href="omcl-20240630.xsd#omcl_ConvertibleDebtSecuritiesAndWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c3a08949-a213-488a-a587-2a4b5d027ce2" xlink:to="loc_omcl_ConvertibleDebtSecuritiesAndWarrantsMember_80cf3b0d-db85-4895-99a9-58b445ebf941" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_4a706ed4-1c9b-4419-86da-c285166d8920" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_NetIncomeLoss_4a706ed4-1c9b-4419-86da-c285166d8920" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_627c520f-5e5d-474e-82de-4a8d46f7a7e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_627c520f-5e5d-474e-82de-4a8d46f7a7e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_ba714e08-a916-4e51-a175-834a2e3a7717" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_ba714e08-a916-4e51-a175-834a2e3a7717" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ceb171db-0b02-4bb9-ab85-b4234d036ce7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ceb171db-0b02-4bb9-ab85-b4234d036ce7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_8d89efc0-5827-4691-8d9d-d8a761fe3c70" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_EarningsPerShareBasic_8d89efc0-5827-4691-8d9d-d8a761fe3c70" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_8b941c83-2e91-44a1-99fd-900abad01892" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_EarningsPerShareDiluted_8b941c83-2e91-44a1-99fd-900abad01892" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_16e80bd9-596d-4c21-a96a-6ddd37b2e8b8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c244599d-a311-443b-abda-04b9c68a3fa1" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_16e80bd9-596d-4c21-a96a-6ddd37b2e8b8" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/CashandCashEquivalentsandFairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#CashandCashEquivalentsandFairValueofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/CashandCashEquivalentsandFairValueofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_269673a8-df06-4edc-80f0-a92b1229b00d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1c0c36a7-5188-4b50-88ea-e77c3248cb7a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_269673a8-df06-4edc-80f0-a92b1229b00d" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1c0c36a7-5188-4b50-88ea-e77c3248cb7a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_fd34fe20-ee5d-49f4-85d7-b9ca4d8005d5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1c0c36a7-5188-4b50-88ea-e77c3248cb7a" xlink:to="loc_us-gaap_DebtInstrumentAxis_fd34fe20-ee5d-49f4-85d7-b9ca4d8005d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fd34fe20-ee5d-49f4-85d7-b9ca4d8005d5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_fd34fe20-ee5d-49f4-85d7-b9ca4d8005d5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fd34fe20-ee5d-49f4-85d7-b9ca4d8005d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3075c489-cd0f-4347-bf3e-75593537566f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_fd34fe20-ee5d-49f4-85d7-b9ca4d8005d5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3075c489-cd0f-4347-bf3e-75593537566f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConvertibleSeniorNotesMember_f045f469-1b28-422c-a455-ac8ba2ea0c05" xlink:href="omcl-20240630.xsd#omcl_ConvertibleSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3075c489-cd0f-4347-bf3e-75593537566f" xlink:to="loc_omcl_ConvertibleSeniorNotesMember_f045f469-1b28-422c-a455-ac8ba2ea0c05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_17e51ee0-9611-487b-959d-07f8bc36740f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1c0c36a7-5188-4b50-88ea-e77c3248cb7a" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_17e51ee0-9611-487b-959d-07f8bc36740f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_17e51ee0-9611-487b-959d-07f8bc36740f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_17e51ee0-9611-487b-959d-07f8bc36740f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_17e51ee0-9611-487b-959d-07f8bc36740f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d352fffa-57f2-4f11-bb1f-83e23acaf783" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_17e51ee0-9611-487b-959d-07f8bc36740f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d352fffa-57f2-4f11-bb1f-83e23acaf783" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_2878c175-6312-48d5-a3a6-320ef44ab789" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d352fffa-57f2-4f11-bb1f-83e23acaf783" xlink:to="loc_us-gaap_ConvertibleDebtMember_2878c175-6312-48d5-a3a6-320ef44ab789" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_137540f4-2f17-45f9-b4b7-3d15c5df3e9a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_269673a8-df06-4edc-80f0-a92b1229b00d" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_137540f4-2f17-45f9-b4b7-3d15c5df3e9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsAtCarryingValue_f39e870f-3b97-4c9a-bb8c-5bfe268b9666" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_269673a8-df06-4edc-80f0-a92b1229b00d" xlink:to="loc_us-gaap_CashEquivalentsAtCarryingValue_f39e870f-3b97-4c9a-bb8c-5bfe268b9666" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_3682598f-6351-484e-bf41-5fcae6c91553" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_269673a8-df06-4edc-80f0-a92b1229b00d" xlink:to="loc_us-gaap_LongTermDebtFairValue_3682598f-6351-484e-bf41-5fcae6c91553" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_7c71cb2b-984d-496d-b058-72df49f58fb7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_269673a8-df06-4edc-80f0-a92b1229b00d" xlink:to="loc_us-gaap_LongTermDebt_7c71cb2b-984d-496d-b058-72df49f58fb7" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/BalanceSheetComponentsAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#BalanceSheetComponentsAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/BalanceSheetComponentsAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_3ef988fd-9159-431b-b87b-b48bde7ccbb5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_29132d3e-7ef8-49f1-b66d-07c15563ded0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_3ef988fd-9159-431b-b87b-b48bde7ccbb5" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_29132d3e-7ef8-49f1-b66d-07c15563ded0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_e21d1ebd-f608-44c6-a8e6-3a86968cf734" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_29132d3e-7ef8-49f1-b66d-07c15563ded0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_e21d1ebd-f608-44c6-a8e6-3a86968cf734" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_e21d1ebd-f608-44c6-a8e6-3a86968cf734_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e21d1ebd-f608-44c6-a8e6-3a86968cf734" xlink:to="loc_us-gaap_EquityComponentDomain_e21d1ebd-f608-44c6-a8e6-3a86968cf734_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_315e0da3-085e-4f42-956c-ab66d2b9f53b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e21d1ebd-f608-44c6-a8e6-3a86968cf734" xlink:to="loc_us-gaap_EquityComponentDomain_315e0da3-085e-4f42-956c-ab66d2b9f53b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_baeb137a-33ce-4f62-b488-a41d216e6da6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_315e0da3-085e-4f42-956c-ab66d2b9f53b" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_baeb137a-33ce-4f62-b488-a41d216e6da6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e0d81b-a123-4e9c-a31e-5d833459df3b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_3ef988fd-9159-431b-b87b-b48bde7ccbb5" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e0d81b-a123-4e9c-a31e-5d833459df3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_f77ab200-8e03-41e3-8b80-8001f1375ca7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e0d81b-a123-4e9c-a31e-5d833459df3b" xlink:to="loc_us-gaap_StockholdersEquity_f77ab200-8e03-41e3-8b80-8001f1375ca7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_190f6e9f-1064-4527-8ead-2e82fce8c1a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e0d81b-a123-4e9c-a31e-5d833459df3b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_190f6e9f-1064-4527-8ead-2e82fce8c1a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_060bae7b-eae7-44f6-943c-03e0d6622e36" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/PropertyandEquipmentPropertyPlantandEquipmentBalancesDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#PropertyandEquipmentPropertyPlantandEquipmentBalancesDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/PropertyandEquipmentPropertyPlantandEquipmentBalancesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_585763d0-d117-46c5-9169-bd8b0e4f80f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3f97cf3f-2662-4200-85a8-7aad3b5f89fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_585763d0-d117-46c5-9169-bd8b0e4f80f4" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3f97cf3f-2662-4200-85a8-7aad3b5f89fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b08fa572-4514-4173-a6d3-86c3617c1348" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3f97cf3f-2662-4200-85a8-7aad3b5f89fe" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b08fa572-4514-4173-a6d3-86c3617c1348" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b08fa572-4514-4173-a6d3-86c3617c1348_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b08fa572-4514-4173-a6d3-86c3617c1348" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b08fa572-4514-4173-a6d3-86c3617c1348_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_78f6888a-9142-4d3d-85b2-53184b8d3f17" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_b08fa572-4514-4173-a6d3-86c3617c1348" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_78f6888a-9142-4d3d-85b2-53184b8d3f17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_598b55f5-4885-4b71-8b83-0fb5e277a6bb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_78f6888a-9142-4d3d-85b2-53184b8d3f17" xlink:to="loc_us-gaap_EquipmentMember_598b55f5-4885-4b71-8b83-0fb5e277a6bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_5578fc53-bc9e-4a2c-9f61-0d96b3029527" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_78f6888a-9142-4d3d-85b2-53184b8d3f17" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_5578fc53-bc9e-4a2c-9f61-0d96b3029527" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdsAndLeaseholdImprovementsMember_6fdd373c-1a50-43b0-87f2-748db05c64a8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LeaseholdsAndLeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_78f6888a-9142-4d3d-85b2-53184b8d3f17" xlink:to="loc_us-gaap_LeaseholdsAndLeaseholdImprovementsMember_6fdd373c-1a50-43b0-87f2-748db05c64a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareDevelopmentMember_e5a0d674-99ae-44d0-b9d2-1e7f740c756e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SoftwareDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_78f6888a-9142-4d3d-85b2-53184b8d3f17" xlink:to="loc_us-gaap_SoftwareDevelopmentMember_e5a0d674-99ae-44d0-b9d2-1e7f740c756e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_fc47cb3e-ffa6-4942-a08a-a6acb7e73f06" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_78f6888a-9142-4d3d-85b2-53184b8d3f17" xlink:to="loc_us-gaap_ConstructionInProgressMember_fc47cb3e-ffa6-4942-a08a-a6acb7e73f06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_c65aa248-93fe-4bf1-b3af-ef58a3ed6d94" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_585763d0-d117-46c5-9169-bd8b0e4f80f4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_c65aa248-93fe-4bf1-b3af-ef58a3ed6d94" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_c9218406-ec2a-4cd5-a701-2829ebd7fe6f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_585763d0-d117-46c5-9169-bd8b0e4f80f4" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_c9218406-ec2a-4cd5-a701-2829ebd7fe6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_8bcfc4d2-fcf5-454b-9fec-d8046361e5af" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_585763d0-d117-46c5-9169-bd8b0e4f80f4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_8bcfc4d2-fcf5-454b-9fec-d8046361e5af" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/PropertyandEquipmentGeographicInformationforPropertyandEquipmentNetDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#PropertyandEquipmentGeographicInformationforPropertyandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/PropertyandEquipmentGeographicInformationforPropertyandEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ed2aa46a-0538-4e37-b808-d84c1966ce4e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_6d266637-a3ff-4aa4-9f9c-fcc9b438204e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ed2aa46a-0538-4e37-b808-d84c1966ce4e" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_6d266637-a3ff-4aa4-9f9c-fcc9b438204e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_6d45a64a-8663-4620-bae4-70d66e9f7656" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_6d266637-a3ff-4aa4-9f9c-fcc9b438204e" xlink:to="loc_srt_StatementGeographicalAxis_6d45a64a-8663-4620-bae4-70d66e9f7656" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_6d45a64a-8663-4620-bae4-70d66e9f7656_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_6d45a64a-8663-4620-bae4-70d66e9f7656" xlink:to="loc_srt_SegmentGeographicalDomain_6d45a64a-8663-4620-bae4-70d66e9f7656_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_a3705137-8521-4151-9709-250ee00085ad" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_6d45a64a-8663-4620-bae4-70d66e9f7656" xlink:to="loc_srt_SegmentGeographicalDomain_a3705137-8521-4151-9709-250ee00085ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_c4819ccf-683c-4748-96f4-b08f24051cfc" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_a3705137-8521-4151-9709-250ee00085ad" xlink:to="loc_country_US_c4819ccf-683c-4748-96f4-b08f24051cfc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_2cd576f9-1d6c-47f1-8c7f-77b2a611aeae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_a3705137-8521-4151-9709-250ee00085ad" xlink:to="loc_us-gaap_NonUsMember_2cd576f9-1d6c-47f1-8c7f-77b2a611aeae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_9f16adca-f3ed-4f5f-b417-d1ef8a5e6944" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ed2aa46a-0538-4e37-b808-d84c1966ce4e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_9f16adca-f3ed-4f5f-b417-d1ef8a5e6944" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/GoodwillandIntangibleAssetsCarryingAmountsandUsefulLivesofIntangibleAssetsDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#GoodwillandIntangibleAssetsCarryingAmountsandUsefulLivesofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/GoodwillandIntangibleAssetsCarryingAmountsandUsefulLivesofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_9a05cbb7-36f9-4a35-a356-adcde16d8984" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_97f3123d-ffb3-4205-9201-6b0e772b1945" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_9a05cbb7-36f9-4a35-a356-adcde16d8984" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_97f3123d-ffb3-4205-9201-6b0e772b1945" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1db0e3d5-bca5-4c99-b3bb-ee45e35504fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_97f3123d-ffb3-4205-9201-6b0e772b1945" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1db0e3d5-bca5-4c99-b3bb-ee45e35504fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1db0e3d5-bca5-4c99-b3bb-ee45e35504fb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1db0e3d5-bca5-4c99-b3bb-ee45e35504fb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1db0e3d5-bca5-4c99-b3bb-ee45e35504fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0cff62d-4ee6-40e0-87e0-d2385c1b685a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1db0e3d5-bca5-4c99-b3bb-ee45e35504fb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0cff62d-4ee6-40e0-87e0-d2385c1b685a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_50f84059-ed92-469f-973f-9841be2aa665" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0cff62d-4ee6-40e0-87e0-d2385c1b685a" xlink:to="loc_us-gaap_CustomerRelationshipsMember_50f84059-ed92-469f-973f-9841be2aa665" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_02354810-1726-41cf-82fb-4ca2a0ae9385" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0cff62d-4ee6-40e0-87e0-d2385c1b685a" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_02354810-1726-41cf-82fb-4ca2a0ae9385" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrderOrProductionBacklogMember_5fb33008-a941-4d88-875a-201a3818a894" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OrderOrProductionBacklogMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0cff62d-4ee6-40e0-87e0-d2385c1b685a" xlink:to="loc_us-gaap_OrderOrProductionBacklogMember_5fb33008-a941-4d88-875a-201a3818a894" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_6fefe961-fc1b-4fc0-becf-cfb7f24ad1b3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0cff62d-4ee6-40e0-87e0-d2385c1b685a" xlink:to="loc_us-gaap_TradeNamesMember_6fefe961-fc1b-4fc0-becf-cfb7f24ad1b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_2256d59d-61f8-48e8-bcf2-f7bc512e7dc2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e0cff62d-4ee6-40e0-87e0-d2385c1b685a" xlink:to="loc_us-gaap_PatentsMember_2256d59d-61f8-48e8-bcf2-f7bc512e7dc2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_a99103e5-e91c-4e6b-92bd-8bc3d02ec687" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_97f3123d-ffb3-4205-9201-6b0e772b1945" xlink:to="loc_srt_RangeAxis_a99103e5-e91c-4e6b-92bd-8bc3d02ec687" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a99103e5-e91c-4e6b-92bd-8bc3d02ec687_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_a99103e5-e91c-4e6b-92bd-8bc3d02ec687" xlink:to="loc_srt_RangeMember_a99103e5-e91c-4e6b-92bd-8bc3d02ec687_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_496b13a0-1904-488b-9cc9-5ef95b6886c9" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_a99103e5-e91c-4e6b-92bd-8bc3d02ec687" xlink:to="loc_srt_RangeMember_496b13a0-1904-488b-9cc9-5ef95b6886c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_2f23be33-691e-4126-91f5-793fb2b37d95" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_496b13a0-1904-488b-9cc9-5ef95b6886c9" xlink:to="loc_srt_MinimumMember_2f23be33-691e-4126-91f5-793fb2b37d95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_16215fa3-6d6e-4a99-b8e6-3a3ba437f7a1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_496b13a0-1904-488b-9cc9-5ef95b6886c9" xlink:to="loc_srt_MaximumMember_16215fa3-6d6e-4a99-b8e6-3a3ba437f7a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_bcbb6f4d-a060-454d-a043-507849afa5a3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_9a05cbb7-36f9-4a35-a356-adcde16d8984" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_bcbb6f4d-a060-454d-a043-507849afa5a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_91eb542f-f244-417d-a7bf-07c9923b28db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_9a05cbb7-36f9-4a35-a356-adcde16d8984" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_91eb542f-f244-417d-a7bf-07c9923b28db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss_56908d1a-32b0-4861-8b03-5481a2a85999" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_9a05cbb7-36f9-4a35-a356-adcde16d8984" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss_56908d1a-32b0-4861-8b03-5481a2a85999" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_2188977c-ed6c-4068-9ee8-efb2f3ee5306" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_9a05cbb7-36f9-4a35-a356-adcde16d8984" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_2188977c-ed6c-4068-9ee8-efb2f3ee5306" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_7a5760ef-f15f-4264-9246-2e2318aeca8d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_9a05cbb7-36f9-4a35-a356-adcde16d8984" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_7a5760ef-f15f-4264-9246-2e2318aeca8d" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/DebtandCreditAgreementDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#DebtandCreditAgreementDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/DebtandCreditAgreementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_0bb06168-487b-46d6-80c7-02e58ee7d6ab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_DebtInstrumentTable_0bb06168-487b-46d6-80c7-02e58ee7d6ab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_69297d83-2cdb-4b81-b112-0d62324f63ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0bb06168-487b-46d6-80c7-02e58ee7d6ab" xlink:to="loc_us-gaap_CreditFacilityAxis_69297d83-2cdb-4b81-b112-0d62324f63ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_69297d83-2cdb-4b81-b112-0d62324f63ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_69297d83-2cdb-4b81-b112-0d62324f63ae" xlink:to="loc_us-gaap_CreditFacilityDomain_69297d83-2cdb-4b81-b112-0d62324f63ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_edf7bb79-913d-433d-ab0c-d9e2b6c5195d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_69297d83-2cdb-4b81-b112-0d62324f63ae" xlink:to="loc_us-gaap_CreditFacilityDomain_edf7bb79-913d-433d-ab0c-d9e2b6c5195d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_2a9d56c0-cbcf-4d81-ad5c-5a19a694274d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_edf7bb79-913d-433d-ab0c-d9e2b6c5195d" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_2a9d56c0-cbcf-4d81-ad5c-5a19a694274d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_IncrementalLoanFacilityMember_93f4ed37-b69f-44ee-816d-78a6bae4d285" xlink:href="omcl-20240630.xsd#omcl_IncrementalLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_edf7bb79-913d-433d-ab0c-d9e2b6c5195d" xlink:to="loc_omcl_IncrementalLoanFacilityMember_93f4ed37-b69f-44ee-816d-78a6bae4d285" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_907e83c9-eb9e-4789-bebf-dc93e98338b4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_edf7bb79-913d-433d-ab0c-d9e2b6c5195d" xlink:to="loc_us-gaap_LetterOfCreditMember_907e83c9-eb9e-4789-bebf-dc93e98338b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BridgeLoanMember_67b0498a-e73f-4d12-b3ab-20ff64df3d2d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BridgeLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_edf7bb79-913d-433d-ab0c-d9e2b6c5195d" xlink:to="loc_us-gaap_BridgeLoanMember_67b0498a-e73f-4d12-b3ab-20ff64df3d2d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_dc7fc240-6bd1-426d-a857-26c960c4b927" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0bb06168-487b-46d6-80c7-02e58ee7d6ab" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_dc7fc240-6bd1-426d-a857-26c960c4b927" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_dc7fc240-6bd1-426d-a857-26c960c4b927_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_dc7fc240-6bd1-426d-a857-26c960c4b927" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_dc7fc240-6bd1-426d-a857-26c960c4b927_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_12dd393b-ff2d-4fbb-b729-17c682d80597" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_dc7fc240-6bd1-426d-a857-26c960c4b927" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_12dd393b-ff2d-4fbb-b729-17c682d80597" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_WellsFargoSecuritiesLLCCitizensBankNAAndJPMorganChaseBankNAMember_af9b369f-9435-40f7-a396-688783a25e6f" xlink:href="omcl-20240630.xsd#omcl_WellsFargoSecuritiesLLCCitizensBankNAAndJPMorganChaseBankNAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_12dd393b-ff2d-4fbb-b729-17c682d80597" xlink:to="loc_omcl_WellsFargoSecuritiesLLCCitizensBankNAAndJPMorganChaseBankNAMember_af9b369f-9435-40f7-a396-688783a25e6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_WellsFargoSecuritiesLLCJPMorganChaseBankNAPNCCapitalMarketsLLCAndTDSecuritiesUSALLCMember_818bbbf4-5d55-4a90-8cb6-35a127adf7a2" xlink:href="omcl-20240630.xsd#omcl_WellsFargoSecuritiesLLCJPMorganChaseBankNAPNCCapitalMarketsLLCAndTDSecuritiesUSALLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_12dd393b-ff2d-4fbb-b729-17c682d80597" xlink:to="loc_omcl_WellsFargoSecuritiesLLCJPMorganChaseBankNAPNCCapitalMarketsLLCAndTDSecuritiesUSALLCMember_818bbbf4-5d55-4a90-8cb6-35a127adf7a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_157d9596-f870-454b-a047-3274993ea4ca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0bb06168-487b-46d6-80c7-02e58ee7d6ab" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_157d9596-f870-454b-a047-3274993ea4ca" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_157d9596-f870-454b-a047-3274993ea4ca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_157d9596-f870-454b-a047-3274993ea4ca" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_157d9596-f870-454b-a047-3274993ea4ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ed2b0328-0d16-4664-a92b-7f48fbe431d9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_157d9596-f870-454b-a047-3274993ea4ca" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ed2b0328-0d16-4664-a92b-7f48fbe431d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_e7b830b0-76cb-4238-9091-469a941fc454" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ed2b0328-0d16-4664-a92b-7f48fbe431d9" xlink:to="loc_us-gaap_LineOfCreditMember_e7b830b0-76cb-4238-9091-469a941fc454" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_3f708fe7-32eb-449b-afb6-f9d56ff63951" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0bb06168-487b-46d6-80c7-02e58ee7d6ab" xlink:to="loc_srt_RangeAxis_3f708fe7-32eb-449b-afb6-f9d56ff63951" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3f708fe7-32eb-449b-afb6-f9d56ff63951_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_3f708fe7-32eb-449b-afb6-f9d56ff63951" xlink:to="loc_srt_RangeMember_3f708fe7-32eb-449b-afb6-f9d56ff63951_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a884b83c-a111-4244-b5bc-b981bd601c92" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_3f708fe7-32eb-449b-afb6-f9d56ff63951" xlink:to="loc_srt_RangeMember_a884b83c-a111-4244-b5bc-b981bd601c92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_94232179-7eac-4260-b570-e3788ba74cb6" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a884b83c-a111-4244-b5bc-b981bd601c92" xlink:to="loc_srt_MinimumMember_94232179-7eac-4260-b570-e3788ba74cb6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_aad680d6-c5b5-457f-833f-be077fffd12d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a884b83c-a111-4244-b5bc-b981bd601c92" xlink:to="loc_srt_MaximumMember_aad680d6-c5b5-457f-833f-be077fffd12d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_c995114d-d540-4b65-bc35-28356eb1c557" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0bb06168-487b-46d6-80c7-02e58ee7d6ab" xlink:to="loc_us-gaap_VariableRateAxis_c995114d-d540-4b65-bc35-28356eb1c557" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_c995114d-d540-4b65-bc35-28356eb1c557_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_c995114d-d540-4b65-bc35-28356eb1c557" xlink:to="loc_us-gaap_VariableRateDomain_c995114d-d540-4b65-bc35-28356eb1c557_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_75eff5f9-30c9-47a1-ae04-c6bd569510d3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_c995114d-d540-4b65-bc35-28356eb1c557" xlink:to="loc_us-gaap_VariableRateDomain_75eff5f9-30c9-47a1-ae04-c6bd569510d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_SecuredOvernightFinancingRateSOFRApplicableMarginMember_9083d87b-d37f-46a7-a763-656f54d059e6" xlink:href="omcl-20240630.xsd#omcl_SecuredOvernightFinancingRateSOFRApplicableMarginMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_75eff5f9-30c9-47a1-ae04-c6bd569510d3" xlink:to="loc_omcl_SecuredOvernightFinancingRateSOFRApplicableMarginMember_9083d87b-d37f-46a7-a763-656f54d059e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsEffectiveSwapRateMember_74a1cd07-ad46-4d18-9fe6-61ed077b4aca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FederalFundsEffectiveSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_75eff5f9-30c9-47a1-ae04-c6bd569510d3" xlink:to="loc_us-gaap_FederalFundsEffectiveSwapRateMember_74a1cd07-ad46-4d18-9fe6-61ed077b4aca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_OneMonthSecuredOvernightFinancingRateSOFRMember_67565dc1-7cb2-419f-b3ab-4784ac9d54ad" xlink:href="omcl-20240630.xsd#omcl_OneMonthSecuredOvernightFinancingRateSOFRMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_75eff5f9-30c9-47a1-ae04-c6bd569510d3" xlink:to="loc_omcl_OneMonthSecuredOvernightFinancingRateSOFRMember_67565dc1-7cb2-419f-b3ab-4784ac9d54ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_OneMonthSecuredOvernightFinancingRateSOFRApplicableMarginMember_13a8ab07-0dea-4647-a319-f9cfc28ef238" xlink:href="omcl-20240630.xsd#omcl_OneMonthSecuredOvernightFinancingRateSOFRApplicableMarginMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_75eff5f9-30c9-47a1-ae04-c6bd569510d3" xlink:to="loc_omcl_OneMonthSecuredOvernightFinancingRateSOFRApplicableMarginMember_13a8ab07-0dea-4647-a319-f9cfc28ef238" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_153ed277-2da4-4241-86b9-e7419a03b3e6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_DebtInstrumentTerm_153ed277-2da4-4241-86b9-e7419a03b3e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_700b2274-3aae-4a63-9cd2-805dd062587a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_700b2274-3aae-4a63-9cd2-805dd062587a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption_a0465473-ae54-4601-9798-017ca013d4fc" xlink:href="omcl-20240630.xsd#omcl_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_omcl_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption_a0465473-ae54-4601-9798-017ca013d4fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentCovenantAdjustedEBITDAThreshold_277c3cf4-2d63-461e-9527-ae7c9743a911" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentCovenantAdjustedEBITDAThreshold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_omcl_DebtInstrumentCovenantAdjustedEBITDAThreshold_277c3cf4-2d63-461e-9527-ae7c9743a911" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_4e42e676-a0d0-41f6-b536-3c094c615303" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_4e42e676-a0d0-41f6-b536-3c094c615303" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_c61da799-dd42-4d04-9429-8385e553d08e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_c61da799-dd42-4d04-9429-8385e553d08e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentCovenantMaximumSecuredNetLeverageRatio_2f1aea15-7d79-4027-a293-afc2f673053e" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentCovenantMaximumSecuredNetLeverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_omcl_DebtInstrumentCovenantMaximumSecuredNetLeverageRatio_2f1aea15-7d79-4027-a293-afc2f673053e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentCovenantMinimumInterestCoverageRatio_01a997e0-63a5-4dc0-9258-1348ffa9514f" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentCovenantMinimumInterestCoverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_omcl_DebtInstrumentCovenantMinimumInterestCoverageRatio_01a997e0-63a5-4dc0-9258-1348ffa9514f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross_0c63c6dd-8a0a-4563-abc1-92e333b7aeaa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross_0c63c6dd-8a0a-4563-abc1-92e333b7aeaa" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_4dc87c00-7e2c-4c63-a829-e4feac02d9fd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_4dc87c00-7e2c-4c63-a829-e4feac02d9fd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_9cca0e45-d217-45ce-8e6b-c1f6ae096fa1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1460ae41-c840-4852-9cf0-43ad7e9028e5" xlink:to="loc_us-gaap_LongTermDebt_9cca0e45-d217-45ce-8e6b-c1f6ae096fa1" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotesNarrativeDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#ConvertibleSeniorNotesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/ConvertibleSeniorNotesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_926f720a-4f69-4306-9637-00de65bbcbee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentTable_926f720a-4f69-4306-9637-00de65bbcbee" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9daa39f7-9aa7-4bb3-9465-fb4f9000f0c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_926f720a-4f69-4306-9637-00de65bbcbee" xlink:to="loc_us-gaap_DebtInstrumentAxis_9daa39f7-9aa7-4bb3-9465-fb4f9000f0c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9daa39f7-9aa7-4bb3-9465-fb4f9000f0c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9daa39f7-9aa7-4bb3-9465-fb4f9000f0c7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9daa39f7-9aa7-4bb3-9465-fb4f9000f0c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a4fd3b9b-2ab0-43aa-9ba1-d07bdba485e8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9daa39f7-9aa7-4bb3-9465-fb4f9000f0c7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a4fd3b9b-2ab0-43aa-9ba1-d07bdba485e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConvertibleSeniorNotesMember_6b0e69ac-b553-49e9-a793-8fe0025e2d6f" xlink:href="omcl-20240630.xsd#omcl_ConvertibleSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a4fd3b9b-2ab0-43aa-9ba1-d07bdba485e8" xlink:to="loc_omcl_ConvertibleSeniorNotesMember_6b0e69ac-b553-49e9-a793-8fe0025e2d6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_0219b842-2cb8-4b40-839b-0831636b3118" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_926f720a-4f69-4306-9637-00de65bbcbee" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_0219b842-2cb8-4b40-839b-0831636b3118" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0219b842-2cb8-4b40-839b-0831636b3118_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0219b842-2cb8-4b40-839b-0831636b3118" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0219b842-2cb8-4b40-839b-0831636b3118_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_de0b5679-c6b3-4d81-8f7e-047970a09ed4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0219b842-2cb8-4b40-839b-0831636b3118" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_de0b5679-c6b3-4d81-8f7e-047970a09ed4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_87c4747d-655a-4c7a-b12e-91bcd8554420" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_de0b5679-c6b3-4d81-8f7e-047970a09ed4" xlink:to="loc_us-gaap_ConvertibleDebtMember_87c4747d-655a-4c7a-b12e-91bcd8554420" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_67b05aa4-8f74-4f8e-b4a2-a1b34dd498cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_926f720a-4f69-4306-9637-00de65bbcbee" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_67b05aa4-8f74-4f8e-b4a2-a1b34dd498cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_67b05aa4-8f74-4f8e-b4a2-a1b34dd498cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_67b05aa4-8f74-4f8e-b4a2-a1b34dd498cd" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_67b05aa4-8f74-4f8e-b4a2-a1b34dd498cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_e3a3ca37-e568-4fb0-95f6-7d640cfe0ec5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_67b05aa4-8f74-4f8e-b4a2-a1b34dd498cd" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_e3a3ca37-e568-4fb0-95f6-7d640cfe0ec5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_a4048ff0-092e-4d5d-a420-692d936d4995" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_e3a3ca37-e568-4fb0-95f6-7d640cfe0ec5" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_a4048ff0-092e-4d5d-a420-692d936d4995" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_c6307f3b-2aa9-4a22-9f5f-52c07d5c6c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_e3a3ca37-e568-4fb0-95f6-7d640cfe0ec5" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_c6307f3b-2aa9-4a22-9f5f-52c07d5c6c4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_d6782a3f-54fe-4ed7-b0ae-ec949d4d51db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_926f720a-4f69-4306-9637-00de65bbcbee" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_d6782a3f-54fe-4ed7-b0ae-ec949d4d51db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_d6782a3f-54fe-4ed7-b0ae-ec949d4d51db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_d6782a3f-54fe-4ed7-b0ae-ec949d4d51db" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_d6782a3f-54fe-4ed7-b0ae-ec949d4d51db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_6d707a34-1cb1-47f5-b250-0a353ad0cfc6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_d6782a3f-54fe-4ed7-b0ae-ec949d4d51db" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_6d707a34-1cb1-47f5-b250-0a353ad0cfc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConvertibleNoteHedgeRightsMember_5ec19075-54ca-43c2-92ee-d26d46521849" xlink:href="omcl-20240630.xsd#omcl_ConvertibleNoteHedgeRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_6d707a34-1cb1-47f5-b250-0a353ad0cfc6" xlink:to="loc_omcl_ConvertibleNoteHedgeRightsMember_5ec19075-54ca-43c2-92ee-d26d46521849" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_c01d51fb-4db3-4a05-8e35-206a0c022c57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_6d707a34-1cb1-47f5-b250-0a353ad0cfc6" xlink:to="loc_us-gaap_WarrantMember_c01d51fb-4db3-4a05-8e35-206a0c022c57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_6be1d583-8228-48fa-aad7-696711c79288" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_926f720a-4f69-4306-9637-00de65bbcbee" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_6be1d583-8228-48fa-aad7-696711c79288" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_6be1d583-8228-48fa-aad7-696711c79288_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6be1d583-8228-48fa-aad7-696711c79288" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_6be1d583-8228-48fa-aad7-696711c79288_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_c2539a3e-e5e6-42d3-826f-54ce72346f9d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6be1d583-8228-48fa-aad7-696711c79288" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_c2539a3e-e5e6-42d3-826f-54ce72346f9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockOptionMember_5f98cede-0bf8-452c-8a45-ffca2611ce3b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_c2539a3e-e5e6-42d3-826f-54ce72346f9d" xlink:to="loc_us-gaap_StockOptionMember_5f98cede-0bf8-452c-8a45-ffca2611ce3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_345fa5b0-4325-42d6-b5e6-1ace4748f585" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_345fa5b0-4325-42d6-b5e6-1ace4748f585" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_44edc2ed-f9ff-4178-bb0e-cfdf47145e70" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_44edc2ed-f9ff-4178-bb0e-cfdf47145e70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentAccordionFeatureIncreaseLimit_eca14e85-24b8-48e8-9b6a-9eb2fff3856d" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_DebtInstrumentAccordionFeatureIncreaseLimit_eca14e85-24b8-48e8-9b6a-9eb2fff3856d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromConvertibleDebt_f50f5653-44f7-4f94-a899-d275bed7f452" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_ProceedsFromConvertibleDebt_f50f5653-44f7-4f94-a899-d275bed7f452" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_08f1317d-8cfc-405e-8dab-5ac16b11a921" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_08f1317d-8cfc-405e-8dab-5ac16b11a921" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_b574c036-cb36-48ca-beef-a7be808a9d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_b574c036-cb36-48ca-beef-a7be808a9d5b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_042e3625-dc7a-45b7-8420-d81472b012f7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_042e3625-dc7a-45b7-8420-d81472b012f7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_222c40f6-6339-4667-ba16-a819662d0a3e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_222c40f6-6339-4667-ba16-a819662d0a3e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentConvertiblePrincipalAmountOfNotesMinimum_edbfdfd3-8d51-4edf-bc4b-860643e157ea" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentConvertiblePrincipalAmountOfNotesMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_DebtInstrumentConvertiblePrincipalAmountOfNotesMinimum_edbfdfd3-8d51-4edf-bc4b-860643e157ea" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentConvertibleMaximumCash_1e874118-d0a1-4e38-a6e5-cab9001806cc" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentConvertibleMaximumCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_DebtInstrumentConvertibleMaximumCash_1e874118-d0a1-4e38-a6e5-cab9001806cc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentConvertibleConsiderationInExcessAmount_2c4c4a53-41a2-4468-99fc-954735e933ca" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentConvertibleConsiderationInExcessAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_DebtInstrumentConvertibleConsiderationInExcessAmount_2c4c4a53-41a2-4468-99fc-954735e933ca" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_25d2e6f1-bd1e-4cd0-8416-65122d5d8a62" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_25d2e6f1-bd1e-4cd0-8416-65122d5d8a62" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_c723a51f-5244-4ec9-a760-87cba49b0fa1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_c723a51f-5244-4ec9-a760-87cba49b0fa1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_60b8ddc3-7d08-46ad-b08f-63034cfba1cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_60b8ddc3-7d08-46ad-b08f-63034cfba1cd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentRedemptionFaceAmountOfNotesThatMustBeOutstanding_dda14351-16a1-4b63-aa8d-5e231e24e6d3" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentRedemptionFaceAmountOfNotesThatMustBeOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_DebtInstrumentRedemptionFaceAmountOfNotesThatMustBeOutstanding_dda14351-16a1-4b63-aa8d-5e231e24e6d3" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6c494390-b1c6-441e-96cd-e1c33dc9c76b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6c494390-b1c6-441e-96cd-e1c33dc9c76b" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_10945fb1-40ee-471a-b23b-652e154a5e21" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_10945fb1-40ee-471a-b23b-652e154a5e21" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DebtInstrumentConvertibleNumberOfSharesIssuable_acf5185e-c070-4ad3-92d8-ba292e74b999" xlink:href="omcl-20240630.xsd#omcl_DebtInstrumentConvertibleNumberOfSharesIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_DebtInstrumentConvertibleNumberOfSharesIssuable_acf5185e-c070-4ad3-92d8-ba292e74b999" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_fbde7836-b3de-44d5-b306-6af860205882" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_fbde7836-b3de-44d5-b306-6af860205882" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_627e1be7-6bad-4a7a-851d-706e9683df37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_627e1be7-6bad-4a7a-851d-706e9683df37" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_AdjustmentsToAdditionalPaidInCapitalConvertibleNoteHedge_2e53d99d-913e-485f-99d3-a8b3c65bf577" xlink:href="omcl-20240630.xsd#omcl_AdjustmentsToAdditionalPaidInCapitalConvertibleNoteHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_AdjustmentsToAdditionalPaidInCapitalConvertibleNoteHedge_2e53d99d-913e-485f-99d3-a8b3c65bf577" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_DeferredTaxAssetConvertibleDebtHedge_fa2ccfa1-e3e2-4943-8441-34ee3c9d4548" xlink:href="omcl-20240630.xsd#omcl_DeferredTaxAssetConvertibleDebtHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_omcl_DeferredTaxAssetConvertibleDebtHedge_fa2ccfa1-e3e2-4943-8441-34ee3c9d4548" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfWarrants_83441405-f8a3-45dd-978b-b801cf936569" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromIssuanceOfWarrants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_09185809-4160-4e57-93b3-689d5e13872b" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfWarrants_83441405-f8a3-45dd-978b-b801cf936569" xlink:type="arc" order="22"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotesConvertibleDebtBalancesDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#ConvertibleSeniorNotesConvertibleDebtBalancesDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/ConvertibleSeniorNotesConvertibleDebtBalancesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_3aaebec6-224f-4a4a-9c1d-45cd8343f09f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_ffa6daf4-8988-4b86-9ae9-f335af3de28f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3aaebec6-224f-4a4a-9c1d-45cd8343f09f" xlink:to="loc_us-gaap_DebtInstrumentTable_ffa6daf4-8988-4b86-9ae9-f335af3de28f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_7309563b-7195-494c-807b-564e699c4a7e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ffa6daf4-8988-4b86-9ae9-f335af3de28f" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_7309563b-7195-494c-807b-564e699c4a7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_7309563b-7195-494c-807b-564e699c4a7e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7309563b-7195-494c-807b-564e699c4a7e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_7309563b-7195-494c-807b-564e699c4a7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_213677a9-e4d8-4f8d-95bc-86bbf6e24b16" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7309563b-7195-494c-807b-564e699c4a7e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_213677a9-e4d8-4f8d-95bc-86bbf6e24b16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_69d66b85-6169-4084-8953-287eb08a81ac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_213677a9-e4d8-4f8d-95bc-86bbf6e24b16" xlink:to="loc_us-gaap_ConvertibleDebtMember_69d66b85-6169-4084-8953-287eb08a81ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_4d783217-6ee4-4c27-bfa8-9ecfd944bd12" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ffa6daf4-8988-4b86-9ae9-f335af3de28f" xlink:to="loc_us-gaap_DebtInstrumentAxis_4d783217-6ee4-4c27-bfa8-9ecfd944bd12" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4d783217-6ee4-4c27-bfa8-9ecfd944bd12_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_4d783217-6ee4-4c27-bfa8-9ecfd944bd12" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4d783217-6ee4-4c27-bfa8-9ecfd944bd12_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_274ecd07-a435-4a30-a55b-b39f5642ebed" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_4d783217-6ee4-4c27-bfa8-9ecfd944bd12" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_274ecd07-a435-4a30-a55b-b39f5642ebed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConvertibleSeniorNotesMember_7f7b9b8b-eb2d-4459-9f3d-d7cad12e2b40" xlink:href="omcl-20240630.xsd#omcl_ConvertibleSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_274ecd07-a435-4a30-a55b-b39f5642ebed" xlink:to="loc_omcl_ConvertibleSeniorNotesMember_7f7b9b8b-eb2d-4459-9f3d-d7cad12e2b40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_197ef4fd-cdaf-4172-b5a5-9ba348777041" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3aaebec6-224f-4a4a-9c1d-45cd8343f09f" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_197ef4fd-cdaf-4172-b5a5-9ba348777041" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_03614ba9-d206-419b-9cca-e3cd37a5861d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3aaebec6-224f-4a4a-9c1d-45cd8343f09f" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_03614ba9-d206-419b-9cca-e3cd37a5861d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_749994e1-63f8-49a8-bf34-3675f9f4f0f5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3aaebec6-224f-4a4a-9c1d-45cd8343f09f" xlink:to="loc_us-gaap_LongTermDebt_749994e1-63f8-49a8-bf34-3675f9f4f0f5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotesComponentsofInterestExpenseDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#ConvertibleSeniorNotesComponentsofInterestExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/ConvertibleSeniorNotesComponentsofInterestExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_ca76b7ea-1994-4604-9c8f-33feb8fc7145" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_2495321a-fc34-4885-b436-bc805580ce08" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ca76b7ea-1994-4604-9c8f-33feb8fc7145" xlink:to="loc_us-gaap_DebtInstrumentTable_2495321a-fc34-4885-b436-bc805580ce08" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_48807380-f7e3-4fb5-b837-4077ebf9b61b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2495321a-fc34-4885-b436-bc805580ce08" xlink:to="loc_us-gaap_DebtInstrumentAxis_48807380-f7e3-4fb5-b837-4077ebf9b61b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_48807380-f7e3-4fb5-b837-4077ebf9b61b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_48807380-f7e3-4fb5-b837-4077ebf9b61b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_48807380-f7e3-4fb5-b837-4077ebf9b61b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_31e9dafe-e3ec-4ee6-8879-a588a2ad504b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_48807380-f7e3-4fb5-b837-4077ebf9b61b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_31e9dafe-e3ec-4ee6-8879-a588a2ad504b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ConvertibleSeniorNotesMember_f6527ab1-4212-4826-8dff-08b306b0c7b5" xlink:href="omcl-20240630.xsd#omcl_ConvertibleSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_31e9dafe-e3ec-4ee6-8879-a588a2ad504b" xlink:to="loc_omcl_ConvertibleSeniorNotesMember_f6527ab1-4212-4826-8dff-08b306b0c7b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_38858b29-06df-4eff-ae6b-9abf304546fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2495321a-fc34-4885-b436-bc805580ce08" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_38858b29-06df-4eff-ae6b-9abf304546fb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_38858b29-06df-4eff-ae6b-9abf304546fb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_38858b29-06df-4eff-ae6b-9abf304546fb" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_38858b29-06df-4eff-ae6b-9abf304546fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ddba58c4-bd4f-491a-97c6-d8c7bfa2c41c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_38858b29-06df-4eff-ae6b-9abf304546fb" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ddba58c4-bd4f-491a-97c6-d8c7bfa2c41c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_4e21afae-8054-4c56-90d2-25d506e15ce9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ddba58c4-bd4f-491a-97c6-d8c7bfa2c41c" xlink:to="loc_us-gaap_ConvertibleDebtMember_4e21afae-8054-4c56-90d2-25d506e15ce9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_975b0a5f-4cdc-4d60-9585-09747c708ac0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ca76b7ea-1994-4604-9c8f-33feb8fc7145" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_975b0a5f-4cdc-4d60-9585-09747c708ac0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_22698c2b-45bf-4bfa-b825-768e81cc1633" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ca76b7ea-1994-4604-9c8f-33feb8fc7145" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_22698c2b-45bf-4bfa-b825-768e81cc1633" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/LessorLeasesNarrativeDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#LessorLeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/LessorLeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorLeaseDescriptionLineItems_d21ae1b9-c915-4a98-975d-c9dc207d01cb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LessorLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorLeaseDescriptionTable_8df23bb5-c18f-483b-b6dd-77b91e4562f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LessorLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_d21ae1b9-c915-4a98-975d-c9dc207d01cb" xlink:to="loc_us-gaap_LessorLeaseDescriptionTable_8df23bb5-c18f-483b-b6dd-77b91e4562f3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_11e5d676-a314-41df-a002-9798f519827f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LessorLeaseDescriptionTable_8df23bb5-c18f-483b-b6dd-77b91e4562f3" xlink:to="loc_srt_RangeAxis_11e5d676-a314-41df-a002-9798f519827f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_11e5d676-a314-41df-a002-9798f519827f_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_11e5d676-a314-41df-a002-9798f519827f" xlink:to="loc_srt_RangeMember_11e5d676-a314-41df-a002-9798f519827f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_12a37676-4db1-47f4-9c89-80aac935f6e6" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_11e5d676-a314-41df-a002-9798f519827f" xlink:to="loc_srt_RangeMember_12a37676-4db1-47f4-9c89-80aac935f6e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_de0827d3-6ed3-4136-bebe-2ed4aa7ac377" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_12a37676-4db1-47f4-9c89-80aac935f6e6" xlink:to="loc_srt_MinimumMember_de0827d3-6ed3-4136-bebe-2ed4aa7ac377" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1606d01d-b3e0-401d-8f60-88233bbf7236" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_12a37676-4db1-47f4-9c89-80aac935f6e6" xlink:to="loc_srt_MaximumMember_1606d01d-b3e0-401d-8f60-88233bbf7236" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorSalesTypeLeaseTermOfContract1_232ab516-f4c5-4421-a97b-e91f1a1e61fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LessorSalesTypeLeaseTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_d21ae1b9-c915-4a98-975d-c9dc207d01cb" xlink:to="loc_us-gaap_LessorSalesTypeLeaseTermOfContract1_232ab516-f4c5-4421-a97b-e91f1a1e61fb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/LesseeLeasesNarrativeDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#LesseeLeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/LesseeLeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_a87f630a-cbd5-45c3-99a6-5a660cb41576" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_a7ea2cb5-f14c-4ee0-a1f9-8f8f5191b1ff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_a87f630a-cbd5-45c3-99a6-5a660cb41576" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_a7ea2cb5-f14c-4ee0-a1f9-8f8f5191b1ff" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_aab8b78e-1918-4bcb-b9e9-8a7e3c424626" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_a7ea2cb5-f14c-4ee0-a1f9-8f8f5191b1ff" xlink:to="loc_srt_RangeAxis_aab8b78e-1918-4bcb-b9e9-8a7e3c424626" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_aab8b78e-1918-4bcb-b9e9-8a7e3c424626_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_aab8b78e-1918-4bcb-b9e9-8a7e3c424626" xlink:to="loc_srt_RangeMember_aab8b78e-1918-4bcb-b9e9-8a7e3c424626_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_177f6679-a142-4633-9bc9-6c1c1500e955" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_aab8b78e-1918-4bcb-b9e9-8a7e3c424626" xlink:to="loc_srt_RangeMember_177f6679-a142-4633-9bc9-6c1c1500e955" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_ab586589-a688-4a58-beb9-f2ad3b2418dc" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_177f6679-a142-4633-9bc9-6c1c1500e955" xlink:to="loc_srt_MinimumMember_ab586589-a688-4a58-beb9-f2ad3b2418dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_269aadba-852c-4b7b-b420-80d1a725f561" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_177f6679-a142-4633-9bc9-6c1c1500e955" xlink:to="loc_srt_MaximumMember_269aadba-852c-4b7b-b420-80d1a725f561" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_f8f87312-b7d6-4578-a835-669bd59125ab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_a87f630a-cbd5-45c3-99a6-5a660cb41576" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_f8f87312-b7d6-4578-a835-669bd59125ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_a78ebcd3-1cd6-4ff5-86d6-e775bbfef588" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_a87f630a-cbd5-45c3-99a6-5a660cb41576" xlink:to="loc_us-gaap_OperatingLeaseCost_a78ebcd3-1cd6-4ff5-86d6-e775bbfef588" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseImpairmentLoss_e057373d-705f-407d-886d-ce296cd75b37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_a87f630a-cbd5-45c3-99a6-5a660cb41576" xlink:to="loc_us-gaap_OperatingLeaseImpairmentLoss_e057373d-705f-407d-886d-ce296cd75b37" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSharedbasedCompensationExpenseDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationSharedbasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSharedbasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_bc0a7f1d-fee6-489f-91df-4b612bdf198d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_e2565ada-b81d-42d6-a7bb-b8ee97b72d37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_bc0a7f1d-fee6-489f-91df-4b612bdf198d" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_e2565ada-b81d-42d6-a7bb-b8ee97b72d37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_53e989d0-73df-49b2-8bea-a5d15b52c378" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_e2565ada-b81d-42d6-a7bb-b8ee97b72d37" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_53e989d0-73df-49b2-8bea-a5d15b52c378" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_53e989d0-73df-49b2-8bea-a5d15b52c378_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_53e989d0-73df-49b2-8bea-a5d15b52c378" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_53e989d0-73df-49b2-8bea-a5d15b52c378_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_0376ad98-2d4f-448a-86a3-a73a5ceabc92" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_53e989d0-73df-49b2-8bea-a5d15b52c378" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_0376ad98-2d4f-448a-86a3-a73a5ceabc92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_fca70270-e5a0-4f1e-b785-2fbe6c337538" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_0376ad98-2d4f-448a-86a3-a73a5ceabc92" xlink:to="loc_us-gaap_CostOfSalesMember_fca70270-e5a0-4f1e-b785-2fbe6c337538" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_43b39afc-bd04-4c4e-ad3c-a1f4e1243841" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_0376ad98-2d4f-448a-86a3-a73a5ceabc92" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_43b39afc-bd04-4c4e-ad3c-a1f4e1243841" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_8311244f-d4f6-486e-a414-53273da72a87" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_0376ad98-2d4f-448a-86a3-a73a5ceabc92" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_8311244f-d4f6-486e-a414-53273da72a87" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_42da1257-3090-4530-9675-4e8dbd129e2e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_bc0a7f1d-fee6-489f-91df-4b612bdf198d" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_42da1257-3090-4530-9675-4e8dbd129e2e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0010a658-b665-4d54-8b86-517230646c03" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0010a658-b665-4d54-8b86-517230646c03" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_ed75ef1b-0986-4846-82db-1c7b7992c849" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0010a658-b665-4d54-8b86-517230646c03" xlink:to="loc_us-gaap_PlanNameAxis_ed75ef1b-0986-4846-82db-1c7b7992c849" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_ed75ef1b-0986-4846-82db-1c7b7992c849_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_ed75ef1b-0986-4846-82db-1c7b7992c849" xlink:to="loc_us-gaap_PlanNameDomain_ed75ef1b-0986-4846-82db-1c7b7992c849_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_2dd36b00-bcfb-4222-ab05-60231b44cb14" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_ed75ef1b-0986-4846-82db-1c7b7992c849" xlink:to="loc_us-gaap_PlanNameDomain_2dd36b00-bcfb-4222-ab05-60231b44cb14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_A2009PlanMember_b142188a-2217-4152-8a69-f81e660261cc" xlink:href="omcl-20240630.xsd#omcl_A2009PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_2dd36b00-bcfb-4222-ab05-60231b44cb14" xlink:to="loc_omcl_A2009PlanMember_b142188a-2217-4152-8a69-f81e660261cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_7207b587-33c5-45b6-b376-3c240ffd1f29" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0010a658-b665-4d54-8b86-517230646c03" xlink:to="loc_us-gaap_AwardTypeAxis_7207b587-33c5-45b6-b376-3c240ffd1f29" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7207b587-33c5-45b6-b376-3c240ffd1f29_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7207b587-33c5-45b6-b376-3c240ffd1f29" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7207b587-33c5-45b6-b376-3c240ffd1f29_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf92727f-039a-4e5a-ba7d-8a850c408719" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7207b587-33c5-45b6-b376-3c240ffd1f29" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf92727f-039a-4e5a-ba7d-8a850c408719" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_1abcc721-d4f2-403c-a685-e02b0d1d0194" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf92727f-039a-4e5a-ba7d-8a850c408719" xlink:to="loc_us-gaap_EmployeeStockMember_1abcc721-d4f2-403c-a685-e02b0d1d0194" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_b63620a7-ec9d-41a2-952c-18fe1b647373" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf92727f-039a-4e5a-ba7d-8a850c408719" xlink:to="loc_us-gaap_EmployeeStockOptionMember_b63620a7-ec9d-41a2-952c-18fe1b647373" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_768a99e7-67c3-4db0-b2fb-2ac3381b819c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf92727f-039a-4e5a-ba7d-8a850c408719" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_768a99e7-67c3-4db0-b2fb-2ac3381b819c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_c18f47ad-9ee3-4df8-98df-9d8dc5116b01" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf92727f-039a-4e5a-ba7d-8a850c408719" xlink:to="loc_us-gaap_RestrictedStockMember_c18f47ad-9ee3-4df8-98df-9d8dc5116b01" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_125f4449-e9eb-42fe-a3c8-732a39522663" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf92727f-039a-4e5a-ba7d-8a850c408719" xlink:to="loc_us-gaap_PerformanceSharesMember_125f4449-e9eb-42fe-a3c8-732a39522663" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_fb40cedd-3949-44bd-af74-0a8ae093e915" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0010a658-b665-4d54-8b86-517230646c03" xlink:to="loc_srt_ShareRepurchaseProgramAxis_fb40cedd-3949-44bd-af74-0a8ae093e915" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_fb40cedd-3949-44bd-af74-0a8ae093e915_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_fb40cedd-3949-44bd-af74-0a8ae093e915" xlink:to="loc_srt_ShareRepurchaseProgramDomain_fb40cedd-3949-44bd-af74-0a8ae093e915_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_326bb27a-7aa7-43cd-9268-d7b8509c6441" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_fb40cedd-3949-44bd-af74-0a8ae093e915" xlink:to="loc_srt_ShareRepurchaseProgramDomain_326bb27a-7aa7-43cd-9268-d7b8509c6441" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_The2016RepurchaseProgramMember_29d2e248-4e1d-4da4-88e3-3148f559719f" xlink:href="omcl-20240630.xsd#omcl_The2016RepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_326bb27a-7aa7-43cd-9268-d7b8509c6441" xlink:to="loc_omcl_The2016RepurchaseProgramMember_29d2e248-4e1d-4da4-88e3-3148f559719f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_d0e5bebb-8acb-4239-9564-019c5da3e077" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_d0e5bebb-8acb-4239-9564-019c5da3e077" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_391c9984-38ab-4cbe-b15e-719160ba4ec5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_391c9984-38ab-4cbe-b15e-719160ba4ec5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsPurchasedInPeriodWeightedAveragePrice_eab5f3ef-9b14-43ca-959a-3f9ccc3356f3" xlink:href="omcl-20240630.xsd#omcl_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsPurchasedInPeriodWeightedAveragePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_omcl_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsPurchasedInPeriodWeightedAveragePrice_eab5f3ef-9b14-43ca-959a-3f9ccc3356f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_cfc5687e-9f68-4f3f-9755-a8058cb6f027" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_cfc5687e-9f68-4f3f-9755-a8058cb6f027" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_dcff9015-5bf1-4ef7-83a1-9aae4d3d0522" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_dcff9015-5bf1-4ef7-83a1-9aae4d3d0522" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_0eb690cc-602d-42f5-9e7a-9ed6fc3f3e9e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_0eb690cc-602d-42f5-9e7a-9ed6fc3f3e9e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_308d2956-a74c-4866-812c-a9802433e7b6" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_308d2956-a74c-4866-812c-a9802433e7b6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_1617bb5a-9140-4fe7-99d1-bd2fc9025ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_1617bb5a-9140-4fe7-99d1-bd2fc9025ba4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_3741693c-68d0-4da7-a186-c57f18b3a385" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9dbd09b7-9665-4429-a820-ef1497988223" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_3741693c-68d0-4da7-a186-c57f18b3a385" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueESPPSharesDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueESPPSharesDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueESPPSharesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_fee06322-ca05-4a4f-95d2-ad66a479ff84" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_fee06322-ca05-4a4f-95d2-ad66a479ff84" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_d321462a-0ea2-4981-bd05-78adc5a0a7db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_fee06322-ca05-4a4f-95d2-ad66a479ff84" xlink:to="loc_us-gaap_AwardTypeAxis_d321462a-0ea2-4981-bd05-78adc5a0a7db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d321462a-0ea2-4981-bd05-78adc5a0a7db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_d321462a-0ea2-4981-bd05-78adc5a0a7db" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d321462a-0ea2-4981-bd05-78adc5a0a7db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5ef7ec13-b379-4c3b-a456-b62d50e6e931" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_d321462a-0ea2-4981-bd05-78adc5a0a7db" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5ef7ec13-b379-4c3b-a456-b62d50e6e931" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_435247a3-4eec-40f8-999c-c2f7aa486f31" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5ef7ec13-b379-4c3b-a456-b62d50e6e931" xlink:to="loc_us-gaap_EmployeeStockMember_435247a3-4eec-40f8-999c-c2f7aa486f31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_ef973785-0d3e-4ee2-908a-341b848aa511" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_fee06322-ca05-4a4f-95d2-ad66a479ff84" xlink:to="loc_srt_RangeAxis_ef973785-0d3e-4ee2-908a-341b848aa511" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ef973785-0d3e-4ee2-908a-341b848aa511_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_ef973785-0d3e-4ee2-908a-341b848aa511" xlink:to="loc_srt_RangeMember_ef973785-0d3e-4ee2-908a-341b848aa511_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b878392a-bd4e-4c1c-a4c8-32ec01439b0b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_ef973785-0d3e-4ee2-908a-341b848aa511" xlink:to="loc_srt_RangeMember_b878392a-bd4e-4c1c-a4c8-32ec01439b0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_98fec2fd-1daa-403a-ba4c-af55e7c37508" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b878392a-bd4e-4c1c-a4c8-32ec01439b0b" xlink:to="loc_srt_MinimumMember_98fec2fd-1daa-403a-ba4c-af55e7c37508" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_5edc8196-acd8-426d-aec4-aefd07319990" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b878392a-bd4e-4c1c-a4c8-32ec01439b0b" xlink:to="loc_srt_MaximumMember_5edc8196-acd8-426d-aec4-aefd07319990" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_1894d552-0d3a-463f-a211-e72c7e139623" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_1894d552-0d3a-463f-a211-e72c7e139623" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_f9ef91f7-e436-4513-8da7-aeebe4db2686" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_f9ef91f7-e436-4513-8da7-aeebe4db2686" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_f845c77c-d690-4d4b-99aa-4e16c83ef00a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_f845c77c-d690-4d4b-99aa-4e16c83ef00a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_498fd87f-11c4-4653-8668-3b5ae0c6b6c5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_498fd87f-11c4-4653-8668-3b5ae0c6b6c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_972c2b17-33c1-4175-acbf-189d724ec8bf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_972c2b17-33c1-4175-acbf-189d724ec8bf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_ecb149f7-53d1-44d1-a704-cca9f97f24a9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d8f174b3-28ce-4476-b974-b802158fe089" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_ecb149f7-53d1-44d1-a704-cca9f97f24a9" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueStockOptionsGrantedDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueStockOptionsGrantedDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueStockOptionsGrantedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5a6a535b-6b76-4c4d-aadf-1794c12e4f79" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_66f62acc-1abb-46ae-a007-2f5566e3e3b2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5a6a535b-6b76-4c4d-aadf-1794c12e4f79" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_66f62acc-1abb-46ae-a007-2f5566e3e3b2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_7829e0e4-60b6-4781-85a1-6895c4e41d40" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_66f62acc-1abb-46ae-a007-2f5566e3e3b2" xlink:to="loc_us-gaap_AwardTypeAxis_7829e0e4-60b6-4781-85a1-6895c4e41d40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7829e0e4-60b6-4781-85a1-6895c4e41d40_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7829e0e4-60b6-4781-85a1-6895c4e41d40" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7829e0e4-60b6-4781-85a1-6895c4e41d40_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0660ee7d-62af-4d2f-a634-81535e24e766" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7829e0e4-60b6-4781-85a1-6895c4e41d40" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0660ee7d-62af-4d2f-a634-81535e24e766" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_708108ba-f80e-4783-9b5a-7fddb2f9f174" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0660ee7d-62af-4d2f-a634-81535e24e766" xlink:to="loc_us-gaap_EmployeeStockOptionMember_708108ba-f80e-4783-9b5a-7fddb2f9f174" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_e019454c-0112-438b-a3d8-e86d7ae7d7ad" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5a6a535b-6b76-4c4d-aadf-1794c12e4f79" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_e019454c-0112-438b-a3d8-e86d7ae7d7ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_239813ee-0127-47e3-937e-bcc0229fd146" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5a6a535b-6b76-4c4d-aadf-1794c12e4f79" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_239813ee-0127-47e3-937e-bcc0229fd146" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_c721514c-e655-4af9-a563-8cfec6eeecef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5a6a535b-6b76-4c4d-aadf-1794c12e4f79" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_c721514c-e655-4af9-a563-8cfec6eeecef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsEstimatedForfeitureRate_80ecb32b-45d0-4421-9ebf-9baf4725d1a6" xlink:href="omcl-20240630.xsd#omcl_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsEstimatedForfeitureRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5a6a535b-6b76-4c4d-aadf-1794c12e4f79" xlink:to="loc_omcl_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsEstimatedForfeitureRate_80ecb32b-45d0-4421-9ebf-9baf4725d1a6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_2601cd0a-b196-49c9-85bc-dbd8abffc423" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5a6a535b-6b76-4c4d-aadf-1794c12e4f79" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_2601cd0a-b196-49c9-85bc-dbd8abffc423" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationShareOptionActivityDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationShareOptionActivityDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationShareOptionActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c842c8b-8843-44da-91ee-8f28df122626" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c842c8b-8843-44da-91ee-8f28df122626" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_af4513df-805f-4be2-87cc-385e6f48e290" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c842c8b-8843-44da-91ee-8f28df122626" xlink:to="loc_us-gaap_PlanNameAxis_af4513df-805f-4be2-87cc-385e6f48e290" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_af4513df-805f-4be2-87cc-385e6f48e290_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_af4513df-805f-4be2-87cc-385e6f48e290" xlink:to="loc_us-gaap_PlanNameDomain_af4513df-805f-4be2-87cc-385e6f48e290_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_08266bff-91c7-460e-9bb3-7ddf58025361" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_af4513df-805f-4be2-87cc-385e6f48e290" xlink:to="loc_us-gaap_PlanNameDomain_08266bff-91c7-460e-9bb3-7ddf58025361" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_A2009PlanMember_90929140-0112-4520-9a15-0c401a17c314" xlink:href="omcl-20240630.xsd#omcl_A2009PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_08266bff-91c7-460e-9bb3-7ddf58025361" xlink:to="loc_omcl_A2009PlanMember_90929140-0112-4520-9a15-0c401a17c314" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_a9612d07-4040-4309-806c-1ccf0edadd2a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_a9612d07-4040-4309-806c-1ccf0edadd2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_0a54a796-1b58-4b81-b063-3831f3c24bce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_a9612d07-4040-4309-806c-1ccf0edadd2a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_0a54a796-1b58-4b81-b063-3831f3c24bce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_4480e884-6e2c-43d3-84a6-a2e518727204" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_a9612d07-4040-4309-806c-1ccf0edadd2a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_4480e884-6e2c-43d3-84a6-a2e518727204" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_0252dbb3-e919-41a9-b943-f47b566979d0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_a9612d07-4040-4309-806c-1ccf0edadd2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_0252dbb3-e919-41a9-b943-f47b566979d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod_455a61d0-89f0-4fb8-9292-fa849fb8a8b3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_a9612d07-4040-4309-806c-1ccf0edadd2a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod_455a61d0-89f0-4fb8-9292-fa849fb8a8b3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_9a9ba674-8b89-47f4-ba49-9de5dde2acf2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_a9612d07-4040-4309-806c-1ccf0edadd2a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_9a9ba674-8b89-47f4-ba49-9de5dde2acf2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_b3641231-7971-4b11-adfb-681d1baec841" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber_b8d55e34-0c90-453d-9f3f-dfb046a55961" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber_b8d55e34-0c90-453d-9f3f-dfb046a55961" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_d8777272-d913-43d3-a7e6-c83a245f6aa6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_d8777272-d913-43d3-a7e6-c83a245f6aa6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d283880b-1922-445f-9feb-20a7d1901998" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d283880b-1922-445f-9feb-20a7d1901998" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_ec28335b-be01-4c49-8c8e-337c5460d786" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d283880b-1922-445f-9feb-20a7d1901998" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_ec28335b-be01-4c49-8c8e-337c5460d786" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_d9cd59b8-0a6f-41f7-9092-ee9c6d1f7a02" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d283880b-1922-445f-9feb-20a7d1901998" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_d9cd59b8-0a6f-41f7-9092-ee9c6d1f7a02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_b2c47218-8e68-471e-80b3-3d48d5de5dde" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d283880b-1922-445f-9feb-20a7d1901998" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_b2c47218-8e68-471e-80b3-3d48d5de5dde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_97693207-3cf1-42f7-b372-afbcb415b510" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d283880b-1922-445f-9feb-20a7d1901998" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_97693207-3cf1-42f7-b372-afbcb415b510" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_45a123fb-fb59-45d6-8a1c-a941ebd7f336" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d283880b-1922-445f-9feb-20a7d1901998" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_45a123fb-fb59-45d6-8a1c-a941ebd7f336" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_56f487f7-0250-476f-94c4-20c72b4ede06" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice_5b21c6ce-1567-4079-9ab4-e8e0f4c11be9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice_5b21c6ce-1567-4079-9ab4-e8e0f4c11be9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_4629f6d3-0c42-40d1-854f-ce87a44f21a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_4629f6d3-0c42-40d1-854f-ce87a44f21a0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract_e780ac70-6565-4de7-b60f-f3df50075295" xlink:href="omcl-20240630.xsd#omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract_e780ac70-6565-4de7-b60f-f3df50075295" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_c48042e1-4eb3-4730-b560-0623542cb3c2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract_e780ac70-6565-4de7-b60f-f3df50075295" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_c48042e1-4eb3-4730-b560-0623542cb3c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1_181602bf-5563-43ce-8894-b216dc18a46c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract_e780ac70-6565-4de7-b60f-f3df50075295" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1_181602bf-5563-43ce-8894-b216dc18a46c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_d537788d-d54d-4bec-8861-eb190fee2513" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract_e780ac70-6565-4de7-b60f-f3df50075295" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_d537788d-d54d-4bec-8861-eb190fee2513" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract_dccd8f62-342b-45cd-8621-f403362507e7" xlink:href="omcl-20240630.xsd#omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_318b68ba-f581-4872-9855-c9d62625f077" xlink:to="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract_dccd8f62-342b-45cd-8621-f403362507e7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_1c6b7c8f-67b2-47a8-aa4c-dfde0005d744" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract_dccd8f62-342b-45cd-8621-f403362507e7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_1c6b7c8f-67b2-47a8-aa4c-dfde0005d744" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue_0f8ac9c2-47ef-4001-977e-c9a46b08c998" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract_dccd8f62-342b-45cd-8621-f403362507e7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue_0f8ac9c2-47ef-4001-977e-c9a46b08c998" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_c977d4db-7ec0-4581-89a1-c0d1d1369aa7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract_dccd8f62-342b-45cd-8621-f403362507e7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_c977d4db-7ec0-4581-89a1-c0d1d1369aa7" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationRestrictedStockUnitActivityDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationRestrictedStockUnitActivityDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationRestrictedStockUnitActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9293a96e-b672-476e-aeb3-5776f6f5fa3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c7bf1ffb-a484-4411-b145-5c0c99d513c9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9293a96e-b672-476e-aeb3-5776f6f5fa3a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c7bf1ffb-a484-4411-b145-5c0c99d513c9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_91d2b32e-46c4-4c38-af1f-6deb5f0ab68d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c7bf1ffb-a484-4411-b145-5c0c99d513c9" xlink:to="loc_us-gaap_AwardTypeAxis_91d2b32e-46c4-4c38-af1f-6deb5f0ab68d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_91d2b32e-46c4-4c38-af1f-6deb5f0ab68d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_91d2b32e-46c4-4c38-af1f-6deb5f0ab68d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_91d2b32e-46c4-4c38-af1f-6deb5f0ab68d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_faf6664e-c681-49f8-9773-3c7c2529c9f0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_91d2b32e-46c4-4c38-af1f-6deb5f0ab68d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_faf6664e-c681-49f8-9773-3c7c2529c9f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_42bbe524-2973-44a5-bf1a-bf980450e174" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_faf6664e-c681-49f8-9773-3c7c2529c9f0" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_42bbe524-2973-44a5-bf1a-bf980450e174" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_13d0645b-b041-437c-bfde-9dcdb4b57f9e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c7bf1ffb-a484-4411-b145-5c0c99d513c9" xlink:to="loc_us-gaap_PlanNameAxis_13d0645b-b041-437c-bfde-9dcdb4b57f9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_13d0645b-b041-437c-bfde-9dcdb4b57f9e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_13d0645b-b041-437c-bfde-9dcdb4b57f9e" xlink:to="loc_us-gaap_PlanNameDomain_13d0645b-b041-437c-bfde-9dcdb4b57f9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_6558e8af-89ce-428f-a687-81bb2d7a939c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_13d0645b-b041-437c-bfde-9dcdb4b57f9e" xlink:to="loc_us-gaap_PlanNameDomain_6558e8af-89ce-428f-a687-81bb2d7a939c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_A2009PlanMember_0dbcbf7c-69a3-4e10-9e61-1d6269710c84" xlink:href="omcl-20240630.xsd#omcl_A2009PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_6558e8af-89ce-428f-a687-81bb2d7a939c" xlink:to="loc_omcl_A2009PlanMember_0dbcbf7c-69a3-4e10-9e61-1d6269710c84" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7d290a37-ef2f-488b-b102-337946f9b6c1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9293a96e-b672-476e-aeb3-5776f6f5fa3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7d290a37-ef2f-488b-b102-337946f9b6c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_26217d5e-b628-40ae-9ebc-31404309da10" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7d290a37-ef2f-488b-b102-337946f9b6c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_26217d5e-b628-40ae-9ebc-31404309da10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_e1b67a48-36e4-4023-9d3f-59055b7ecc8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7d290a37-ef2f-488b-b102-337946f9b6c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_e1b67a48-36e4-4023-9d3f-59055b7ecc8c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_4e8816ae-4daa-4158-9511-8daae9939f6c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7d290a37-ef2f-488b-b102-337946f9b6c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_4e8816ae-4daa-4158-9511-8daae9939f6c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_78fe5b8b-1798-4ffc-b2d6-1efd4e68e1ca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7d290a37-ef2f-488b-b102-337946f9b6c1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_78fe5b8b-1798-4ffc-b2d6-1efd4e68e1ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_f8ee29af-ee3d-42ca-a25c-b23b1b587188" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_93a00262-0304-403c-945d-b717398afb17" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9293a96e-b672-476e-aeb3-5776f6f5fa3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_93a00262-0304-403c-945d-b717398afb17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_308fcb1e-948c-485a-bd64-8914ee082006" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_93a00262-0304-403c-945d-b717398afb17" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_308fcb1e-948c-485a-bd64-8914ee082006" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_305bbada-1005-4770-ba2d-a9986c38f449" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_93a00262-0304-403c-945d-b717398afb17" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_305bbada-1005-4770-ba2d-a9986c38f449" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_46f1fa8d-55f4-4845-880c-0e162dd1c805" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_93a00262-0304-403c-945d-b717398afb17" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_46f1fa8d-55f4-4845-880c-0e162dd1c805" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_ec8b70a9-9554-4320-b41c-b7df1774d0d6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_93a00262-0304-403c-945d-b717398afb17" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_ec8b70a9-9554-4320-b41c-b7df1774d0d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_ddd6e6fd-ea97-49c8-a13b-80bd5dde833f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageRemainingTermAbstract_90eef151-7591-4f48-951a-3fa0a6f29d31" xlink:href="omcl-20240630.xsd#omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageRemainingTermAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9293a96e-b672-476e-aeb3-5776f6f5fa3a" xlink:to="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageRemainingTermAbstract_90eef151-7591-4f48-951a-3fa0a6f29d31" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_ac1d8f6f-9674-4ddf-84e4-ef7ff8044195" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageRemainingTermAbstract_90eef151-7591-4f48-951a-3fa0a6f29d31" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_ac1d8f6f-9674-4ddf-84e4-ef7ff8044195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueAbstract_92a3ada2-5e51-4b83-b2d0-b5974177d37e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9293a96e-b672-476e-aeb3-5776f6f5fa3a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueAbstract_92a3ada2-5e51-4b83-b2d0-b5974177d37e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_60b698d0-6864-4b2d-9945-f6ef89f386ba" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueAbstract_92a3ada2-5e51-4b83-b2d0-b5974177d37e" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_60b698d0-6864-4b2d-9945-f6ef89f386ba" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationRestrictedStockAwardActivityDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationRestrictedStockAwardActivityDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationRestrictedStockAwardActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4fc89424-a7ac-4767-9985-70626ffd5406" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_44e3cf5a-3d64-4322-85db-07b7091ff823" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4fc89424-a7ac-4767-9985-70626ffd5406" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_44e3cf5a-3d64-4322-85db-07b7091ff823" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_eed5d00e-2f5c-4d22-acbf-5b723cf0d528" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_44e3cf5a-3d64-4322-85db-07b7091ff823" xlink:to="loc_us-gaap_AwardTypeAxis_eed5d00e-2f5c-4d22-acbf-5b723cf0d528" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_eed5d00e-2f5c-4d22-acbf-5b723cf0d528_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_eed5d00e-2f5c-4d22-acbf-5b723cf0d528" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_eed5d00e-2f5c-4d22-acbf-5b723cf0d528_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d2ea47ae-0d6b-464d-a1e0-61eaa1bfa709" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_eed5d00e-2f5c-4d22-acbf-5b723cf0d528" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d2ea47ae-0d6b-464d-a1e0-61eaa1bfa709" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_d44410bf-c501-4281-abe3-4283001de18f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d2ea47ae-0d6b-464d-a1e0-61eaa1bfa709" xlink:to="loc_us-gaap_RestrictedStockMember_d44410bf-c501-4281-abe3-4283001de18f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_6727279f-bcba-490e-8f25-69c544c90dd3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_44e3cf5a-3d64-4322-85db-07b7091ff823" xlink:to="loc_us-gaap_PlanNameAxis_6727279f-bcba-490e-8f25-69c544c90dd3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_6727279f-bcba-490e-8f25-69c544c90dd3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_6727279f-bcba-490e-8f25-69c544c90dd3" xlink:to="loc_us-gaap_PlanNameDomain_6727279f-bcba-490e-8f25-69c544c90dd3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_a9af3d5d-102f-4512-b737-23318377e854" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_6727279f-bcba-490e-8f25-69c544c90dd3" xlink:to="loc_us-gaap_PlanNameDomain_a9af3d5d-102f-4512-b737-23318377e854" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_A2009PlanMember_53352bfc-74b8-4cc0-8596-2e70715509c3" xlink:href="omcl-20240630.xsd#omcl_A2009PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_a9af3d5d-102f-4512-b737-23318377e854" xlink:to="loc_omcl_A2009PlanMember_53352bfc-74b8-4cc0-8596-2e70715509c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_2067aa54-6ade-47f8-b2d1-1d9d87c3e079" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4fc89424-a7ac-4767-9985-70626ffd5406" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_2067aa54-6ade-47f8-b2d1-1d9d87c3e079" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_d1fb32bb-8c76-4420-b679-51b284a48ced" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_2067aa54-6ade-47f8-b2d1-1d9d87c3e079" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_d1fb32bb-8c76-4420-b679-51b284a48ced" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_e4725d10-3881-4395-8fd7-b0b8b4f7305c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_2067aa54-6ade-47f8-b2d1-1d9d87c3e079" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_e4725d10-3881-4395-8fd7-b0b8b4f7305c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_e51684d9-7d05-4623-8b85-289eddd441fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_2067aa54-6ade-47f8-b2d1-1d9d87c3e079" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_e51684d9-7d05-4623-8b85-289eddd441fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_2ceb6eb4-1635-4390-a842-ffc6c7e421bf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5346c3b0-fb67-485f-b97e-6a676c2b0347" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4fc89424-a7ac-4767-9985-70626ffd5406" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5346c3b0-fb67-485f-b97e-6a676c2b0347" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_0e15f2b6-0d12-4f93-a030-d3baa7b71691" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5346c3b0-fb67-485f-b97e-6a676c2b0347" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_0e15f2b6-0d12-4f93-a030-d3baa7b71691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_ef530595-5f2d-4c84-b8d8-02f984a38556" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5346c3b0-fb67-485f-b97e-6a676c2b0347" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_ef530595-5f2d-4c84-b8d8-02f984a38556" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_8fcdec3a-7b94-4e05-ac00-69d6784203d2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5346c3b0-fb67-485f-b97e-6a676c2b0347" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_8fcdec3a-7b94-4e05-ac00-69d6784203d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_44fd99bf-5806-4bbf-8d74-aec01b9a3c2e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationPerformanceBasedRestrictedStockActivityDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationPerformanceBasedRestrictedStockActivityDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationPerformanceBasedRestrictedStockActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2cd45977-db8e-474b-8ba2-63e817930210" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e83b4f57-d44b-45c9-a358-0be8cce32f34" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2cd45977-db8e-474b-8ba2-63e817930210" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e83b4f57-d44b-45c9-a358-0be8cce32f34" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_f97f2a04-7667-46c0-9196-970aa4deb781" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e83b4f57-d44b-45c9-a358-0be8cce32f34" xlink:to="loc_us-gaap_AwardTypeAxis_f97f2a04-7667-46c0-9196-970aa4deb781" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f97f2a04-7667-46c0-9196-970aa4deb781_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_f97f2a04-7667-46c0-9196-970aa4deb781" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f97f2a04-7667-46c0-9196-970aa4deb781_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b16d5b26-99c3-4ae2-97b3-f99643e6cdcf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_f97f2a04-7667-46c0-9196-970aa4deb781" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b16d5b26-99c3-4ae2-97b3-f99643e6cdcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_2d2ff0b2-6684-483e-a2fc-a68723b0ce41" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b16d5b26-99c3-4ae2-97b3-f99643e6cdcf" xlink:to="loc_us-gaap_PerformanceSharesMember_2d2ff0b2-6684-483e-a2fc-a68723b0ce41" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_08948275-0fbb-4a1a-b6ff-6b332b04c419" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e83b4f57-d44b-45c9-a358-0be8cce32f34" xlink:to="loc_us-gaap_PlanNameAxis_08948275-0fbb-4a1a-b6ff-6b332b04c419" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_08948275-0fbb-4a1a-b6ff-6b332b04c419_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_08948275-0fbb-4a1a-b6ff-6b332b04c419" xlink:to="loc_us-gaap_PlanNameDomain_08948275-0fbb-4a1a-b6ff-6b332b04c419_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_33286c98-8ea7-48ec-8cb6-8887c7928705" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_08948275-0fbb-4a1a-b6ff-6b332b04c419" xlink:to="loc_us-gaap_PlanNameDomain_33286c98-8ea7-48ec-8cb6-8887c7928705" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_A2009PlanMember_977f4c59-e121-4371-9961-099e5edd216c" xlink:href="omcl-20240630.xsd#omcl_A2009PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_33286c98-8ea7-48ec-8cb6-8887c7928705" xlink:to="loc_omcl_A2009PlanMember_977f4c59-e121-4371-9961-099e5edd216c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e6631414-919a-4527-aab2-923b12bb0f32" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2cd45977-db8e-474b-8ba2-63e817930210" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e6631414-919a-4527-aab2-923b12bb0f32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_a0eee6b2-5f4c-43e8-b928-f8ded848dec3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e6631414-919a-4527-aab2-923b12bb0f32" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_a0eee6b2-5f4c-43e8-b928-f8ded848dec3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_ebaf6e94-245e-4550-84fb-709fa018afff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e6631414-919a-4527-aab2-923b12bb0f32" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_ebaf6e94-245e-4550-84fb-709fa018afff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_84455bae-dec5-49ad-9ba7-669c81f93a17" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e6631414-919a-4527-aab2-923b12bb0f32" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_84455bae-dec5-49ad-9ba7-669c81f93a17" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_8d041aca-d775-4592-91f7-1dfb890becb7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_e6631414-919a-4527-aab2-923b12bb0f32" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_8d041aca-d775-4592-91f7-1dfb890becb7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_c834faa6-b9f5-4164-99d3-fd6f140a8e48" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6a54a06a-45f6-47ab-84ca-a87d207da090" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2cd45977-db8e-474b-8ba2-63e817930210" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6a54a06a-45f6-47ab-84ca-a87d207da090" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_a42f5729-5e45-4aaf-a18b-ab7983339c32" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6a54a06a-45f6-47ab-84ca-a87d207da090" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_a42f5729-5e45-4aaf-a18b-ab7983339c32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6e9b2b9f-787e-419f-8eef-aac37b6a9a53" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6a54a06a-45f6-47ab-84ca-a87d207da090" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6e9b2b9f-787e-419f-8eef-aac37b6a9a53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3cbcd3e5-3974-4e68-b9f4-a91fd4c49160" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6a54a06a-45f6-47ab-84ca-a87d207da090" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3cbcd3e5-3974-4e68-b9f4-a91fd4c49160" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_44c58cf6-ec64-4eac-b375-1add2209f96c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6a54a06a-45f6-47ab-84ca-a87d207da090" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_44c58cf6-ec64-4eac-b375-1add2209f96c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_1dcbc5d8-a2a4-41aa-be7d-e5021e949200" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSharesReservedforFutureIssuanceUnderEquityIncentivePlansDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#EmployeeBenefitsandShareBasedCompensationSharesReservedforFutureIssuanceUnderEquityIncentivePlansDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSharesReservedforFutureIssuanceUnderEquityIncentivePlansDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b3a3fcb9-b799-4341-8d07-1811a6fd64a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0a16c2b4-cfc1-49b8-8e74-715b091fc933" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b3a3fcb9-b799-4341-8d07-1811a6fd64a0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0a16c2b4-cfc1-49b8-8e74-715b091fc933" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_465ae1c5-5d19-4922-a9fa-d0e89405f4c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0a16c2b4-cfc1-49b8-8e74-715b091fc933" xlink:to="loc_us-gaap_AwardTypeAxis_465ae1c5-5d19-4922-a9fa-d0e89405f4c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_465ae1c5-5d19-4922-a9fa-d0e89405f4c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_465ae1c5-5d19-4922-a9fa-d0e89405f4c7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_465ae1c5-5d19-4922-a9fa-d0e89405f4c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7c86f45c-351d-4c28-9afa-0141f25e32d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_465ae1c5-5d19-4922-a9fa-d0e89405f4c7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7c86f45c-351d-4c28-9afa-0141f25e32d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_309ac801-b8e0-4ff4-b272-cba736ab4dc1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7c86f45c-351d-4c28-9afa-0141f25e32d7" xlink:to="loc_us-gaap_EmployeeStockOptionMember_309ac801-b8e0-4ff4-b272-cba736ab4dc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_RestrictedStockRSAsRestrictedStockUnitsRSUsAndPreformanceSharesPSUsMember_03170523-23b7-40ad-b666-07ca89360f94" xlink:href="omcl-20240630.xsd#omcl_RestrictedStockRSAsRestrictedStockUnitsRSUsAndPreformanceSharesPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7c86f45c-351d-4c28-9afa-0141f25e32d7" xlink:to="loc_omcl_RestrictedStockRSAsRestrictedStockUnitsRSUsAndPreformanceSharesPSUsMember_03170523-23b7-40ad-b666-07ca89360f94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_FutureGrantsAndAwardsMember_531075a5-d36c-4a55-ba3f-9a1a8eb00a4c" xlink:href="omcl-20240630.xsd#omcl_FutureGrantsAndAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7c86f45c-351d-4c28-9afa-0141f25e32d7" xlink:to="loc_omcl_FutureGrantsAndAwardsMember_531075a5-d36c-4a55-ba3f-9a1a8eb00a4c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_a014dbff-8ad2-4511-bcfa-968091902866" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7c86f45c-351d-4c28-9afa-0141f25e32d7" xlink:to="loc_us-gaap_EmployeeStockMember_a014dbff-8ad2-4511-bcfa-968091902866" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_f38a00df-a606-45b4-9287-671bcf0115c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b3a3fcb9-b799-4341-8d07-1811a6fd64a0" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_f38a00df-a606-45b4-9287-671bcf0115c7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.omnicell.com/role/RestructuringExpensesTotalRestructuringExpenseRecognizedintheCondensedConsolidatedStatementsofOperationsDetails" xlink:type="simple" xlink:href="omcl-20240630.xsd#RestructuringExpensesTotalRestructuringExpenseRecognizedintheCondensedConsolidatedStatementsofOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.omnicell.com/role/RestructuringExpensesTotalRestructuringExpenseRecognizedintheCondensedConsolidatedStatementsofOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_18c6300d-ae1a-4082-946c-808aa545a364" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_f59b10c4-cead-415b-b01c-9836f9bb646c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_18c6300d-ae1a-4082-946c-808aa545a364" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_f59b10c4-cead-415b-b01c-9836f9bb646c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_c9e4373e-2f35-4089-a318-0650f2d61227" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_f59b10c4-cead-415b-b01c-9836f9bb646c" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_c9e4373e-2f35-4089-a318-0650f2d61227" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_c9e4373e-2f35-4089-a318-0650f2d61227_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_c9e4373e-2f35-4089-a318-0650f2d61227" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_c9e4373e-2f35-4089-a318-0650f2d61227_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_f09639f6-bf7e-41a8-ad6b-34925bb2aabf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_c9e4373e-2f35-4089-a318-0650f2d61227" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_f09639f6-bf7e-41a8-ad6b-34925bb2aabf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_36a6d3db-8739-44fc-81b6-42a7ccb51ca3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_f09639f6-bf7e-41a8-ad6b-34925bb2aabf" xlink:to="loc_us-gaap_CostOfSalesMember_36a6d3db-8739-44fc-81b6-42a7ccb51ca3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_8d7f5fad-9054-4706-8732-04f6fdf6fc9c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_f09639f6-bf7e-41a8-ad6b-34925bb2aabf" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_8d7f5fad-9054-4706-8732-04f6fdf6fc9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_76a4f547-b6bf-4aa2-a6a5-699340136f94" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_f09639f6-bf7e-41a8-ad6b-34925bb2aabf" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_76a4f547-b6bf-4aa2-a6a5-699340136f94" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_0436a96d-887c-48f2-977a-99ccfc5a6fa0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_18c6300d-ae1a-4082-946c-808aa545a364" xlink:to="loc_us-gaap_RestructuringCharges_0436a96d-887c-48f2-977a-99ccfc5a6fa0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_EmployeeStockMember" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockMember" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_PerformanceSharesMember" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_RestrictedStockRSAsRestrictedStockUnitsRSUsAndPreformanceSharesPSUsMember_fff2a84c-0117-435a-9cc6-6a496a66d6af" xlink:href="omcl-20240630.xsd#omcl_RestrictedStockRSAsRestrictedStockUnitsRSUsAndPreformanceSharesPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_omcl_RestrictedStockRSAsRestrictedStockUnitsRSUsAndPreformanceSharesPSUsMember_fff2a84c-0117-435a-9cc6-6a496a66d6af" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_omcl_FutureGrantsAndAwardsMember_d370a455-85b4-46ce-b633-f448ffc4637e" xlink:href="omcl-20240630.xsd#omcl_FutureGrantsAndAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_omcl_FutureGrantsAndAwardsMember_d370a455-85b4-46ce-b633-f448ffc4637e" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-roles-2024.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_OtherAssetsCurrent" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
