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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:45c18be1-cb16-4324-b446-cf6096430404,g:7a1a2a40-81b4-4c01-b08a-ed1987231ad6-->
<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.smithmicro.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="simple" xlink:href="smsi-20230331.xsd#ConsolidatedStatementsofStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="extended" id="i0c083819400842479c9cdad242b175bd_ConsolidatedStatementsofStockholdersEquity">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_7f1b6d33-5ac5-45fa-a8ac-6d67f688db79" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7f1b6d33-5ac5-45fa-a8ac-6d67f688db79" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_ec8c3664-b8e7-4043-8473-825a96f74e06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_CommonStockSharesIssued_ec8c3664-b8e7-4043-8473-825a96f74e06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_8ee75c1f-5f92-4d1e-ad96-a0f564a61c18" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockholdersEquity_8ee75c1f-5f92-4d1e-ad96-a0f564a61c18" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_928dc3b6-3db3-407a-9489-42ffa6bb4fb2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_928dc3b6-3db3-407a-9489-42ffa6bb4fb2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_36acfb66-f56c-4bdb-b221-8f712435f376" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_36acfb66-f56c-4bdb-b221-8f712435f376" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_3466c0e0-fce4-4e3c-821a-114d1fc7b5f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_3466c0e0-fce4-4e3c-821a-114d1fc7b5f6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_1961cc1a-5452-408f-9530-7465d62de2a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_1961cc1a-5452-408f-9530-7465d62de2a0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_458c6c75-e818-47aa-8d72-17f3acc66147" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_458c6c75-e818-47aa-8d72-17f3acc66147" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployeeStockPurchaseProgramRequisiteServicePeriodRecognition_53ea6243-2ed7-49fc-91b9-dd7b6f1aed73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployeeStockPurchaseProgramRequisiteServicePeriodRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployeeStockPurchaseProgramRequisiteServicePeriodRecognition_53ea6243-2ed7-49fc-91b9-dd7b6f1aed73" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_3fb0a9ee-0bd6-428c-8ab7-5da24dabe515" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_3fb0a9ee-0bd6-428c-8ab7-5da24dabe515" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_083be65d-de8e-4f47-8216-58afab710584" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_083be65d-de8e-4f47-8216-58afab710584" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_429951c6-af3e-4eea-938d-da25299e8360" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_429951c6-af3e-4eea-938d-da25299e8360" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_ad5c4579-8e92-4a9f-b3a3-32dfb9cfd259" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_ad5c4579-8e92-4a9f-b3a3-32dfb9cfd259" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_63c6eac5-d5a1-46a8-af14-3b37757fbecd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_63c6eac5-d5a1-46a8-af14-3b37757fbecd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_00715bd3-a3e9-49fb-913e-97701eac4873" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_00715bd3-a3e9-49fb-913e-97701eac4873" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_7662ed77-3357-4e4d-9656-04dce534aac8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_66732e74-8cc7-46f8-8010-b9f7f1bb14ff" xlink:to="loc_us-gaap_NetIncomeLoss_7662ed77-3357-4e4d-9656-04dce534aac8" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_0b27c702-3797-4089-ae3c-7a5cfa21acc5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1e4b792f-7bb9-43e9-b490-f21721a82c03" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c6ec5025-3989-4634-a216-07025f999643" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7f1b6d33-5ac5-45fa-a8ac-6d67f688db79" xlink:to="loc_us-gaap_StatementTable_c6ec5025-3989-4634-a216-07025f999643" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_79b53477-31d1-489a-853f-2c57d7a6981b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c6ec5025-3989-4634-a216-07025f999643" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_79b53477-31d1-489a-853f-2c57d7a6981b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_79b53477-31d1-489a-853f-2c57d7a6981b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_79b53477-31d1-489a-853f-2c57d7a6981b" xlink:to="loc_us-gaap_EquityComponentDomain_79b53477-31d1-489a-853f-2c57d7a6981b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_485be0d5-709a-4ac0-b104-4d82fe54fdea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_79b53477-31d1-489a-853f-2c57d7a6981b" xlink:to="loc_us-gaap_EquityComponentDomain_485be0d5-709a-4ac0-b104-4d82fe54fdea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_788bb61b-0d02-45a1-9fdd-43667460e75e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_485be0d5-709a-4ac0-b104-4d82fe54fdea" xlink:to="loc_us-gaap_CommonStockMember_788bb61b-0d02-45a1-9fdd-43667460e75e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_d975597d-1ab6-4fcb-aeb7-2926b0a8d536" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_485be0d5-709a-4ac0-b104-4d82fe54fdea" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_d975597d-1ab6-4fcb-aeb7-2926b0a8d536" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_74d97df8-56b3-4a92-82c4-a1a747064fc4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_485be0d5-709a-4ac0-b104-4d82fe54fdea" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_74d97df8-56b3-4a92-82c4-a1a747064fc4" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/EquityTransactionsDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#EquityTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/EquityTransactionsDetails" xlink:type="extended" id="i87149e3bd5c64fcb8592790032bb13cf_EquityTransactionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_cccd274f-b9c3-4c80-ae45-b4e40b2ef2fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_cccd274f-b9c3-4c80-ae45-b4e40b2ef2fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_31761744-33c7-4592-95dd-c4897ba58dd7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_31761744-33c7-4592-95dd-c4897ba58dd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_989259b6-202c-45d2-b027-adf792b4cce4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_989259b6-202c-45d2-b027-adf792b4cce4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_WarrantsAndRightsOutstandingExercisableTerm_f9b68ec3-caa8-4a58-b10f-814ff3c8f9d4" xlink:href="smsi-20230331.xsd#smsi_WarrantsAndRightsOutstandingExercisableTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_smsi_WarrantsAndRightsOutstandingExercisableTerm_f9b68ec3-caa8-4a58-b10f-814ff3c8f9d4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_6334d3fe-7169-432b-a07d-d8b3aaf767ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_6334d3fe-7169-432b-a07d-d8b3aaf767ff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfPrivatePlacement_049fbff7-a833-481c-a1b6-3c09bd6c9fcd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfPrivatePlacement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfPrivatePlacement_049fbff7-a833-481c-a1b6-3c09bd6c9fcd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_WarrantAndDerivativeLiabilitiesNoncurrent_82dcd3fb-b6b2-4bd2-8298-980688802c82" xlink:href="smsi-20230331.xsd#smsi_WarrantAndDerivativeLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_smsi_WarrantAndDerivativeLiabilitiesNoncurrent_82dcd3fb-b6b2-4bd2-8298-980688802c82" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_624d876e-6611-4509-a7d8-d5db37a82648" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_624d876e-6611-4509-a7d8-d5db37a82648" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightTable_dde2aa5c-27d6-4d75-bfc2-c75da2ef4fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_473ee1fe-00ce-4476-87f5-ffec9b195b79" xlink:to="loc_us-gaap_ClassOfWarrantOrRightTable_dde2aa5c-27d6-4d75-bfc2-c75da2ef4fe9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_f0f0a03c-78f0-4c58-b432-fe607e1985fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_dde2aa5c-27d6-4d75-bfc2-c75da2ef4fe9" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_f0f0a03c-78f0-4c58-b432-fe607e1985fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_f0f0a03c-78f0-4c58-b432-fe607e1985fb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_f0f0a03c-78f0-4c58-b432-fe607e1985fb" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_f0f0a03c-78f0-4c58-b432-fe607e1985fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_7dc6aeb9-d5e9-4ad9-bb69-587733b41517" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_f0f0a03c-78f0-4c58-b432-fe607e1985fb" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_7dc6aeb9-d5e9-4ad9-bb69-587733b41517" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_AdditionalWarrantsMember_b246e76a-cd3c-4b52-8996-9c5a1568a025" xlink:href="smsi-20230331.xsd#smsi_AdditionalWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_7dc6aeb9-d5e9-4ad9-bb69-587733b41517" xlink:to="loc_smsi_AdditionalWarrantsMember_b246e76a-cd3c-4b52-8996-9c5a1568a025" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_68e1bfc5-1499-41ba-9cb9-79837c1cee2c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_dde2aa5c-27d6-4d75-bfc2-c75da2ef4fe9" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_68e1bfc5-1499-41ba-9cb9-79837c1cee2c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_68e1bfc5-1499-41ba-9cb9-79837c1cee2c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_68e1bfc5-1499-41ba-9cb9-79837c1cee2c" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_68e1bfc5-1499-41ba-9cb9-79837c1cee2c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_936109b4-2d26-4860-946c-b5dc3307cb45" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_68e1bfc5-1499-41ba-9cb9-79837c1cee2c" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_936109b4-2d26-4860-946c-b5dc3307cb45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_StockAndAdditionalWarrantsOfferingMember_ca3d7ccf-2bff-4dcb-aa7e-ac3087b2443a" xlink:href="smsi-20230331.xsd#smsi_StockAndAdditionalWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_936109b4-2d26-4860-946c-b5dc3307cb45" xlink:to="loc_smsi_StockAndAdditionalWarrantsOfferingMember_ca3d7ccf-2bff-4dcb-aa7e-ac3087b2443a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_NotesAndWarrantsOfferingMember_8a002366-8b6c-400a-9642-ad8ff9ccefb0" xlink:href="smsi-20230331.xsd#smsi_NotesAndWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_936109b4-2d26-4860-946c-b5dc3307cb45" xlink:to="loc_smsi_NotesAndWarrantsOfferingMember_8a002366-8b6c-400a-9642-ad8ff9ccefb0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_cd7dc07f-e951-4eaa-ba15-f15095c0fd67" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_dde2aa5c-27d6-4d75-bfc2-c75da2ef4fe9" xlink:to="loc_us-gaap_DebtInstrumentAxis_cd7dc07f-e951-4eaa-ba15-f15095c0fd67" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_cd7dc07f-e951-4eaa-ba15-f15095c0fd67_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_cd7dc07f-e951-4eaa-ba15-f15095c0fd67" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_cd7dc07f-e951-4eaa-ba15-f15095c0fd67_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_84610742-3446-4480-af67-39844a5b05cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_cd7dc07f-e951-4eaa-ba15-f15095c0fd67" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_84610742-3446-4480-af67-39844a5b05cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_SeniorSecuredConvertibleNotesMember_566441bc-6ee2-4a47-9eed-05adc9e72cdf" xlink:href="smsi-20230331.xsd#smsi_SeniorSecuredConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_84610742-3446-4480-af67-39844a5b05cb" xlink:to="loc_smsi_SeniorSecuredConvertibleNotesMember_566441bc-6ee2-4a47-9eed-05adc9e72cdf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_307b58e1-f21b-40b9-8d0a-7e521aa7b79e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_dde2aa5c-27d6-4d75-bfc2-c75da2ef4fe9" xlink:to="loc_srt_StatementScenarioAxis_307b58e1-f21b-40b9-8d0a-7e521aa7b79e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_307b58e1-f21b-40b9-8d0a-7e521aa7b79e_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_307b58e1-f21b-40b9-8d0a-7e521aa7b79e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_307b58e1-f21b-40b9-8d0a-7e521aa7b79e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_a78941a7-2798-4870-adf7-5c75f69109d4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_307b58e1-f21b-40b9-8d0a-7e521aa7b79e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_a78941a7-2798-4870-adf7-5c75f69109d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_6ad1021a-8f17-4695-ada9-434ed1d19d79" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_a78941a7-2798-4870-adf7-5c75f69109d4" xlink:to="loc_srt_ScenarioForecastMember_6ad1021a-8f17-4695-ada9-434ed1d19d79" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactionsAdditionalInformationDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#DebtandWarrantsTransactionsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/DebtandWarrantsTransactionsAdditionalInformationDetails" xlink:type="extended" id="ic288b9fda7534f4f82f776b6eb99cc66_DebtandWarrantsTransactionsAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_ConvertibleDebtGross_ca0abf90-c740-4f9d-bdc8-537d1c52b92b" xlink:href="smsi-20230331.xsd#smsi_ConvertibleDebtGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_smsi_ConvertibleDebtGross_ca0abf90-c740-4f9d-bdc8-537d1c52b92b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_2e87c009-b74d-42da-b38d-e5d093b79242" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_2e87c009-b74d-42da-b38d-e5d093b79242" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_fca16486-1230-483c-b798-c174e8d44fd3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_fca16486-1230-483c-b798-c174e8d44fd3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_4aae0cab-cbc4-48d4-acf1-47e53e6c7cd8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_4aae0cab-cbc4-48d4-acf1-47e53e6c7cd8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsOutstandingTerm_aabb0261-8620-49eb-bf40-eceba1825983" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantsAndRightsOutstandingTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_WarrantsAndRightsOutstandingTerm_aabb0261-8620-49eb-bf40-eceba1825983" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d4b4fafb-5ca1-4361-8f18-8082ebb2bbff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d4b4fafb-5ca1-4361-8f18-8082ebb2bbff" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_DebtInstrumentInterestRateDefaultPercentage_c3871a5a-3df8-4b47-a419-193db214b3c8" xlink:href="smsi-20230331.xsd#smsi_DebtInstrumentInterestRateDefaultPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_smsi_DebtInstrumentInterestRateDefaultPercentage_c3871a5a-3df8-4b47-a419-193db214b3c8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_a43c36dc-8b0e-404c-bc92-31da6736496a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_a43c36dc-8b0e-404c-bc92-31da6736496a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_WarrantAndDerivativeLiabilitiesNoncurrent_a7d7036c-bf83-45e5-9a77-936c02e09619" xlink:href="smsi-20230331.xsd#smsi_WarrantAndDerivativeLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_smsi_WarrantAndDerivativeLiabilitiesNoncurrent_a7d7036c-bf83-45e5-9a77-936c02e09619" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_6b40631d-1649-42ed-b13b-6bc2f5dbc0c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_DerivativeLiabilities_6b40631d-1649-42ed-b13b-6bc2f5dbc0c7" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExtinguishmentOfDebtAmount_618b2c4e-260e-4f50-83fb-6f4eada3293a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ExtinguishmentOfDebtAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_ExtinguishmentOfDebtAmount_618b2c4e-260e-4f50-83fb-6f4eada3293a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_511e57e5-ba12-4d1e-a6fe-b40c23f123ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_511e57e5-ba12-4d1e-a6fe-b40c23f123ff" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_9d64bb57-d675-4577-9074-cb567de37c8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_InterestExpenseDebt_9d64bb57-d675-4577-9074-cb567de37c8e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_027025d0-f457-460c-bf98-279793f57322" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_027025d0-f457-460c-bf98-279793f57322" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_d0d3546c-a746-4d44-be17-726f2a4633c1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_d0d3546c-a746-4d44-be17-726f2a4633c1" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_5e6225d2-bce8-4eaf-8fd0-43dfacf374eb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_5e6225d2-bce8-4eaf-8fd0-43dfacf374eb" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_94ef2cf7-4903-432f-9804-50d592f66f47" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_94ef2cf7-4903-432f-9804-50d592f66f47" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_7e3a1fc4-ed8c-45ef-a9ed-d032ce35557a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_fd5f0c48-50c2-4284-8a7a-3266fd48fced" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_7e3a1fc4-ed8c-45ef-a9ed-d032ce35557a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_e8c8384a-1d3e-41da-8dfb-0bebfe558f7e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_7e3a1fc4-ed8c-45ef-a9ed-d032ce35557a" xlink:to="loc_us-gaap_DebtInstrumentAxis_e8c8384a-1d3e-41da-8dfb-0bebfe558f7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e8c8384a-1d3e-41da-8dfb-0bebfe558f7e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_e8c8384a-1d3e-41da-8dfb-0bebfe558f7e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e8c8384a-1d3e-41da-8dfb-0bebfe558f7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_35f6a05f-1e85-4ac6-aab0-9579c203bb6f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_e8c8384a-1d3e-41da-8dfb-0bebfe558f7e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_35f6a05f-1e85-4ac6-aab0-9579c203bb6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_SeniorSecuredConvertibleNotesMember_226e4235-1d4f-4929-a632-b0453eaeb8ef" xlink:href="smsi-20230331.xsd#smsi_SeniorSecuredConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_35f6a05f-1e85-4ac6-aab0-9579c203bb6f" xlink:to="loc_smsi_SeniorSecuredConvertibleNotesMember_226e4235-1d4f-4929-a632-b0453eaeb8ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_10440779-fa43-4f0e-b3c5-fafbecabe915" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_7e3a1fc4-ed8c-45ef-a9ed-d032ce35557a" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_10440779-fa43-4f0e-b3c5-fafbecabe915" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_10440779-fa43-4f0e-b3c5-fafbecabe915_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_10440779-fa43-4f0e-b3c5-fafbecabe915" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_10440779-fa43-4f0e-b3c5-fafbecabe915_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d9260717-4150-413a-a581-8c7b2438357d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_10440779-fa43-4f0e-b3c5-fafbecabe915" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d9260717-4150-413a-a581-8c7b2438357d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_942df014-d97e-4c59-80ca-3822851caf0f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d9260717-4150-413a-a581-8c7b2438357d" xlink:to="loc_us-gaap_ConvertibleDebtMember_942df014-d97e-4c59-80ca-3822851caf0f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_fec60130-e436-4477-b989-6de3c77725d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_7e3a1fc4-ed8c-45ef-a9ed-d032ce35557a" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_fec60130-e436-4477-b989-6de3c77725d9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_fec60130-e436-4477-b989-6de3c77725d9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_fec60130-e436-4477-b989-6de3c77725d9" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_fec60130-e436-4477-b989-6de3c77725d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_e4aad24b-1e79-4e57-bde8-172c469c18a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_fec60130-e436-4477-b989-6de3c77725d9" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_e4aad24b-1e79-4e57-bde8-172c469c18a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_eac59383-70df-4fe9-bce7-79c8fc462be0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_e4aad24b-1e79-4e57-bde8-172c469c18a9" xlink:to="loc_us-gaap_WarrantMember_eac59383-70df-4fe9-bce7-79c8fc462be0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_AdditionalWarrantsMember_6b8dea79-9304-453b-a27b-761ca4d239d5" xlink:href="smsi-20230331.xsd#smsi_AdditionalWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_e4aad24b-1e79-4e57-bde8-172c469c18a9" xlink:to="loc_smsi_AdditionalWarrantsMember_6b8dea79-9304-453b-a27b-761ca4d239d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_8f3ebf65-7dd9-4dbf-96be-f3dc2ea27357" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_7e3a1fc4-ed8c-45ef-a9ed-d032ce35557a" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_8f3ebf65-7dd9-4dbf-96be-f3dc2ea27357" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_8f3ebf65-7dd9-4dbf-96be-f3dc2ea27357_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_8f3ebf65-7dd9-4dbf-96be-f3dc2ea27357" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_8f3ebf65-7dd9-4dbf-96be-f3dc2ea27357_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_06f86b85-6bf2-446a-9d00-4da7f4892700" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_8f3ebf65-7dd9-4dbf-96be-f3dc2ea27357" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_06f86b85-6bf2-446a-9d00-4da7f4892700" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_NotesAndWarrantsOfferingMember_f84002ae-7d0e-4fe3-8c78-e5d7a751e785" xlink:href="smsi-20230331.xsd#smsi_NotesAndWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_06f86b85-6bf2-446a-9d00-4da7f4892700" xlink:to="loc_smsi_NotesAndWarrantsOfferingMember_f84002ae-7d0e-4fe3-8c78-e5d7a751e785" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_StockAndAdditionalWarrantsOfferingMember_2295691f-60d8-4100-a91f-52ae6ad2c668" xlink:href="smsi-20230331.xsd#smsi_StockAndAdditionalWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_06f86b85-6bf2-446a-9d00-4da7f4892700" xlink:to="loc_smsi_StockAndAdditionalWarrantsOfferingMember_2295691f-60d8-4100-a91f-52ae6ad2c668" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_1def6ff4-ea7e-447e-8e6a-46c17289ac96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_7e3a1fc4-ed8c-45ef-a9ed-d032ce35557a" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_1def6ff4-ea7e-447e-8e6a-46c17289ac96" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_1def6ff4-ea7e-447e-8e6a-46c17289ac96_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_1def6ff4-ea7e-447e-8e6a-46c17289ac96" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_1def6ff4-ea7e-447e-8e6a-46c17289ac96_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_0103aa3f-e56d-4f66-96f4-897cc36599c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_1def6ff4-ea7e-447e-8e6a-46c17289ac96" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_0103aa3f-e56d-4f66-96f4-897cc36599c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_30d6a77a-3f33-438c-bb38-de707dc589e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_0103aa3f-e56d-4f66-96f4-897cc36599c2" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_30d6a77a-3f33-438c-bb38-de707dc589e6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactionsAssumptionsDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#DebtandWarrantsTransactionsAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/DebtandWarrantsTransactionsAssumptionsDetails" xlink:type="extended" id="ic68db1bfcdcf4a33abf6358477ec0a36_DebtandWarrantsTransactionsAssumptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_526a2721-e77b-43ba-aa4c-ccbd933e185c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityMeasurementInput_9f2438f7-d583-4d1d-aeaa-b4a8a8227849" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilityMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_526a2721-e77b-43ba-aa4c-ccbd933e185c" xlink:to="loc_us-gaap_DerivativeLiabilityMeasurementInput_9f2438f7-d583-4d1d-aeaa-b4a8a8227849" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsOutstandingMeasurementInput_c13b1ea2-2714-4f77-a26b-dd410113099d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantsAndRightsOutstandingMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_526a2721-e77b-43ba-aa4c-ccbd933e185c" xlink:to="loc_us-gaap_WarrantsAndRightsOutstandingMeasurementInput_c13b1ea2-2714-4f77-a26b-dd410113099d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_8555a94e-9e9b-4e2f-81ae-4864e24b949d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_526a2721-e77b-43ba-aa4c-ccbd933e185c" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_8555a94e-9e9b-4e2f-81ae-4864e24b949d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_595cf230-5c32-495d-a693-6c9ec006787f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_8555a94e-9e9b-4e2f-81ae-4864e24b949d" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_595cf230-5c32-495d-a693-6c9ec006787f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_595cf230-5c32-495d-a693-6c9ec006787f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_595cf230-5c32-495d-a693-6c9ec006787f" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_595cf230-5c32-495d-a693-6c9ec006787f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_51767f09-a0cb-436b-8b77-a9092e17b050" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_595cf230-5c32-495d-a693-6c9ec006787f" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_51767f09-a0cb-436b-8b77-a9092e17b050" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputSharePriceMember_465c1d68-ca6b-457e-8950-5ab0e4001eea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputSharePriceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_51767f09-a0cb-436b-8b77-a9092e17b050" xlink:to="loc_us-gaap_MeasurementInputSharePriceMember_465c1d68-ca6b-457e-8950-5ab0e4001eea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_3db47162-b3cd-4057-8d7d-ce98799438bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_51767f09-a0cb-436b-8b77-a9092e17b050" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_3db47162-b3cd-4057-8d7d-ce98799438bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedDividendRateMember_740ca832-5ed5-4a67-adb1-cf098412891e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputExpectedDividendRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_51767f09-a0cb-436b-8b77-a9092e17b050" xlink:to="loc_us-gaap_MeasurementInputExpectedDividendRateMember_740ca832-5ed5-4a67-adb1-cf098412891e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedTermMember_7b6799dd-f678-4569-9ade-1b10c74e0339" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputExpectedTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_51767f09-a0cb-436b-8b77-a9092e17b050" xlink:to="loc_us-gaap_MeasurementInputExpectedTermMember_7b6799dd-f678-4569-9ade-1b10c74e0339" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputPriceVolatilityMember_b6c5a62d-3f1a-44d9-9af0-5f7270bc66cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputPriceVolatilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_51767f09-a0cb-436b-8b77-a9092e17b050" xlink:to="loc_us-gaap_MeasurementInputPriceVolatilityMember_b6c5a62d-3f1a-44d9-9af0-5f7270bc66cc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_5189462f-c21c-4f6b-bd92-495c1be452ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_8555a94e-9e9b-4e2f-81ae-4864e24b949d" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_5189462f-c21c-4f6b-bd92-495c1be452ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_5189462f-c21c-4f6b-bd92-495c1be452ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_5189462f-c21c-4f6b-bd92-495c1be452ba" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_5189462f-c21c-4f6b-bd92-495c1be452ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_3ce638a7-a2b0-4735-afa0-340eae410ac4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_5189462f-c21c-4f6b-bd92-495c1be452ba" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_3ce638a7-a2b0-4735-afa0-340eae410ac4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_9a7f6988-d871-433e-8a11-71bcbd95696d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_3ce638a7-a2b0-4735-afa0-340eae410ac4" xlink:to="loc_us-gaap_WarrantMember_9a7f6988-d871-433e-8a11-71bcbd95696d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_AdditionalWarrantsMember_6b2d9d25-c16b-40a3-95e9-58d019af3912" xlink:href="smsi-20230331.xsd#smsi_AdditionalWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_3ce638a7-a2b0-4735-afa0-340eae410ac4" xlink:to="loc_smsi_AdditionalWarrantsMember_6b2d9d25-c16b-40a3-95e9-58d019af3912" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_74bcbfa5-bd16-4fe7-977e-d123db46bb91" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_8555a94e-9e9b-4e2f-81ae-4864e24b949d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_74bcbfa5-bd16-4fe7-977e-d123db46bb91" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_74bcbfa5-bd16-4fe7-977e-d123db46bb91_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_74bcbfa5-bd16-4fe7-977e-d123db46bb91" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_74bcbfa5-bd16-4fe7-977e-d123db46bb91_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_1b1dc8cc-05e3-4291-9936-abee35d47fb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_74bcbfa5-bd16-4fe7-977e-d123db46bb91" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_1b1dc8cc-05e3-4291-9936-abee35d47fb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_00e21174-eaf5-44db-8e12-81a2c83ba989" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1b1dc8cc-05e3-4291-9936-abee35d47fb6" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_00e21174-eaf5-44db-8e12-81a2c83ba989" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/FairValueofFinancialInstrumentsLiabilitiesMeasuredatFairValueonaRecurringBasisDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#FairValueofFinancialInstrumentsLiabilitiesMeasuredatFairValueonaRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/FairValueofFinancialInstrumentsLiabilitiesMeasuredatFairValueonaRecurringBasisDetails" xlink:type="extended" id="i11b7c06059d343519f2062c97f804026_FairValueofFinancialInstrumentsLiabilitiesMeasuredatFairValueonaRecurringBasisDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_70eee80a-6273-4642-8972-7ac5a5c0ed8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_e1be44f8-39f5-4134-932d-3edcbccbfaea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_70eee80a-6273-4642-8972-7ac5a5c0ed8e" xlink:to="loc_us-gaap_DerivativeLiabilities_e1be44f8-39f5-4134-932d-3edcbccbfaea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_WarrantsFairValueDisclosure_82a79b69-4633-4708-9fed-ab4ba42de356" xlink:href="smsi-20230331.xsd#smsi_WarrantsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_70eee80a-6273-4642-8972-7ac5a5c0ed8e" xlink:to="loc_smsi_WarrantsFairValueDisclosure_82a79b69-4633-4708-9fed-ab4ba42de356" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_03ae20bd-639b-4efa-9d9a-7fb0dc5de54f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_70eee80a-6273-4642-8972-7ac5a5c0ed8e" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_03ae20bd-639b-4efa-9d9a-7fb0dc5de54f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_79af94b2-3327-4493-94ea-53749a6d2c35" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_70eee80a-6273-4642-8972-7ac5a5c0ed8e" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_79af94b2-3327-4493-94ea-53749a6d2c35" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7ac15f86-9447-4498-8fdb-2f5c992388df" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_79af94b2-3327-4493-94ea-53749a6d2c35" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7ac15f86-9447-4498-8fdb-2f5c992388df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7ac15f86-9447-4498-8fdb-2f5c992388df_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7ac15f86-9447-4498-8fdb-2f5c992388df" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7ac15f86-9447-4498-8fdb-2f5c992388df_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_757044c8-a059-4c93-8cca-763d2df789f1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_7ac15f86-9447-4498-8fdb-2f5c992388df" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_757044c8-a059-4c93-8cca-763d2df789f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_a4c7c4f3-4147-4ead-ae6b-a0311f37a109" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_757044c8-a059-4c93-8cca-763d2df789f1" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_a4c7c4f3-4147-4ead-ae6b-a0311f37a109" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_7ea0e0e9-12c1-4dfc-ad66-938f05819c00" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_79af94b2-3327-4493-94ea-53749a6d2c35" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_7ea0e0e9-12c1-4dfc-ad66-938f05819c00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7ea0e0e9-12c1-4dfc-ad66-938f05819c00_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_7ea0e0e9-12c1-4dfc-ad66-938f05819c00" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7ea0e0e9-12c1-4dfc-ad66-938f05819c00_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_1e191a15-2d3a-4b97-9181-a16450dce7f7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_7ea0e0e9-12c1-4dfc-ad66-938f05819c00" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_1e191a15-2d3a-4b97-9181-a16450dce7f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_3f87f6d4-cf15-405a-b368-48eb8f60d79b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1e191a15-2d3a-4b97-9181-a16450dce7f7" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_3f87f6d4-cf15-405a-b368-48eb8f60d79b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_0f8d9da4-f1cb-42d1-8771-b0d264eb4c6e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_79af94b2-3327-4493-94ea-53749a6d2c35" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_0f8d9da4-f1cb-42d1-8771-b0d264eb4c6e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0f8d9da4-f1cb-42d1-8771-b0d264eb4c6e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_0f8d9da4-f1cb-42d1-8771-b0d264eb4c6e" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0f8d9da4-f1cb-42d1-8771-b0d264eb4c6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f21f827f-27aa-46ed-a19b-c040cabfe946" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_0f8d9da4-f1cb-42d1-8771-b0d264eb4c6e" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f21f827f-27aa-46ed-a19b-c040cabfe946" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_NotesAndWarrantsOfferingMember_0669fc74-cc72-4508-8ac7-597a9534cd84" xlink:href="smsi-20230331.xsd#smsi_NotesAndWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f21f827f-27aa-46ed-a19b-c040cabfe946" xlink:to="loc_smsi_NotesAndWarrantsOfferingMember_0669fc74-cc72-4508-8ac7-597a9534cd84" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_StockAndAdditionalWarrantsOfferingMember_7bff647a-c234-478a-b20e-c51670adc92e" xlink:href="smsi-20230331.xsd#smsi_StockAndAdditionalWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f21f827f-27aa-46ed-a19b-c040cabfe946" xlink:to="loc_smsi_StockAndAdditionalWarrantsOfferingMember_7bff647a-c234-478a-b20e-c51670adc92e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/FairValueofFinancialInstrumentsRollforwardDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#FairValueofFinancialInstrumentsRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/FairValueofFinancialInstrumentsRollforwardDetails" xlink:type="extended" id="ib69dfcfa8f6f40438d25e6c053c2fe35_FairValueofFinancialInstrumentsRollforwardDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_35be4bbd-0f2c-4537-9ed8-67c83b0cb624" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c66d5341-ccaf-4162-9a97-e857acba3202" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_35be4bbd-0f2c-4537-9ed8-67c83b0cb624" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c66d5341-ccaf-4162-9a97-e857acba3202" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-supplement_DerivativeAbstract_c395dd55-a912-40f9-8c53-dfd6d34eaf75" xlink:href="https://xbrl.fasb.org/us-gaap/2022q3/us-gaap-sup-2022q3.xsd#us-gaap_DerivativeAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c66d5341-ccaf-4162-9a97-e857acba3202" xlink:to="loc_us-gaap-supplement_DerivativeAbstract_c395dd55-a912-40f9-8c53-dfd6d34eaf75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_735cb34f-25ed-48f9-b268-c4000caf0279" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-supplement_DerivativeAbstract_c395dd55-a912-40f9-8c53-dfd6d34eaf75" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_735cb34f-25ed-48f9-b268-c4000caf0279" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_ebfa1557-8d02-4add-ae02-872ab580eaa9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-supplement_DerivativeAbstract_c395dd55-a912-40f9-8c53-dfd6d34eaf75" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_ebfa1557-8d02-4add-ae02-872ab580eaa9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossOnDerecognitionOfDebt_967ee10a-cf1c-4740-93bc-716d9febaa7d" xlink:href="smsi-20230331.xsd#smsi_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossOnDerecognitionOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-supplement_DerivativeAbstract_c395dd55-a912-40f9-8c53-dfd6d34eaf75" xlink:to="loc_smsi_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossOnDerecognitionOfDebt_967ee10a-cf1c-4740-93bc-716d9febaa7d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_973f8006-c544-4b10-bc54-fa3cfe71b1e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsNoteDisclosureAbstract_ab4fba18-cdc4-47ab-8cfd-b6627244a767" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantsAndRightsNoteDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c66d5341-ccaf-4162-9a97-e857acba3202" xlink:to="loc_us-gaap_WarrantsAndRightsNoteDisclosureAbstract_ab4fba18-cdc4-47ab-8cfd-b6627244a767" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_3ee0cbce-832b-4849-a01f-82a85228656c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WarrantsAndRightsNoteDisclosureAbstract_ab4fba18-cdc4-47ab-8cfd-b6627244a767" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_3ee0cbce-832b-4849-a01f-82a85228656c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_fe311110-b73c-4f25-8df9-5a59e7ac8515" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WarrantsAndRightsNoteDisclosureAbstract_ab4fba18-cdc4-47ab-8cfd-b6627244a767" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_fe311110-b73c-4f25-8df9-5a59e7ac8515" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_385cd2f1-05ae-4a8a-b4d7-715c0eb55e39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalFairValueElementsAbstract_6f799a37-7b83-41b4-8c57-543d4fa3a8c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalFairValueElementsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c66d5341-ccaf-4162-9a97-e857acba3202" xlink:to="loc_us-gaap_AdditionalFairValueElementsAbstract_6f799a37-7b83-41b4-8c57-543d4fa3a8c7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityValueIncludingDerivativeLiabilities_c80920dc-36f4-4606-9171-c6440fa715b6" xlink:href="smsi-20230331.xsd#smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityValueIncludingDerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdditionalFairValueElementsAbstract_6f799a37-7b83-41b4-8c57-543d4fa3a8c7" xlink:to="loc_smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityValueIncludingDerivativeLiabilities_c80920dc-36f4-4606-9171-c6440fa715b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesGainLossIncludedInEarnings_4a3cfbb4-4944-4931-bd96-f4556e4f54ed" xlink:href="smsi-20230331.xsd#smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdditionalFairValueElementsAbstract_6f799a37-7b83-41b4-8c57-543d4fa3a8c7" xlink:to="loc_smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesGainLossIncludedInEarnings_4a3cfbb4-4944-4931-bd96-f4556e4f54ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesGainLossOnDerecognitionOfDebt_84f7e7d6-76cf-49f9-acb1-001dac2e46d4" xlink:href="smsi-20230331.xsd#smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesGainLossOnDerecognitionOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdditionalFairValueElementsAbstract_6f799a37-7b83-41b4-8c57-543d4fa3a8c7" xlink:to="loc_smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesGainLossOnDerecognitionOfDebt_84f7e7d6-76cf-49f9-acb1-001dac2e46d4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityValueIncludingDerivativeLiabilities_67e96023-33a3-4adf-be0c-8815855b8a3c" xlink:href="smsi-20230331.xsd#smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityValueIncludingDerivativeLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_4a952001-d3d4-43b4-98dd-804797c6bf70" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_35be4bbd-0f2c-4537-9ed8-67c83b0cb624" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_4a952001-d3d4-43b4-98dd-804797c6bf70" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_9adc1412-3a3c-4185-9044-932551234c41" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_4a952001-d3d4-43b4-98dd-804797c6bf70" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_9adc1412-3a3c-4185-9044-932551234c41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_9adc1412-3a3c-4185-9044-932551234c41_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_9adc1412-3a3c-4185-9044-932551234c41" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_9adc1412-3a3c-4185-9044-932551234c41_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0b73d9c7-bdca-4aca-8b5d-61fe612f31ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_9adc1412-3a3c-4185-9044-932551234c41" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0b73d9c7-bdca-4aca-8b5d-61fe612f31ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_NotesAndWarrantsOfferingMember_79120a8b-7bff-4792-a428-39d4c9e67af7" xlink:href="smsi-20230331.xsd#smsi_NotesAndWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0b73d9c7-bdca-4aca-8b5d-61fe612f31ec" xlink:to="loc_smsi_NotesAndWarrantsOfferingMember_79120a8b-7bff-4792-a428-39d4c9e67af7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_StockAndAdditionalWarrantsOfferingMember_d8ad74ac-3ec5-40f0-bce8-c484faef2ce4" xlink:href="smsi-20230331.xsd#smsi_StockAndAdditionalWarrantsOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0b73d9c7-bdca-4aca-8b5d-61fe612f31ec" xlink:to="loc_smsi_StockAndAdditionalWarrantsOfferingMember_d8ad74ac-3ec5-40f0-bce8-c484faef2ce4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/GoodwillandIntangibleAssetsComponentsofIntangibleAssetsDetail" xlink:type="simple" xlink:href="smsi-20230331.xsd#GoodwillandIntangibleAssetsComponentsofIntangibleAssetsDetail"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/GoodwillandIntangibleAssetsComponentsofIntangibleAssetsDetail" xlink:type="extended" id="i22a6a18f8da240709e2ed79e9b1d6301_GoodwillandIntangibleAssetsComponentsofIntangibleAssetsDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8a60f0f7-bdcd-422f-91ae-b235eb6d6391" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_d4334fd1-f8d5-406d-842b-3131eb9c530b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8a60f0f7-bdcd-422f-91ae-b235eb6d6391" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_d4334fd1-f8d5-406d-842b-3131eb9c530b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_e102ae7b-dab0-444b-aa0d-bff75b049a70" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8a60f0f7-bdcd-422f-91ae-b235eb6d6391" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_e102ae7b-dab0-444b-aa0d-bff75b049a70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_6f03522d-18df-46ab-99a2-e3361afc81e5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8a60f0f7-bdcd-422f-91ae-b235eb6d6391" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_6f03522d-18df-46ab-99a2-e3361afc81e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FiniteLivedIntangibleAssetsBeforeImpairment_cebcb04d-e122-470f-b973-402d1542c270" xlink:href="smsi-20230331.xsd#smsi_FiniteLivedIntangibleAssetsBeforeImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8a60f0f7-bdcd-422f-91ae-b235eb6d6391" xlink:to="loc_smsi_FiniteLivedIntangibleAssetsBeforeImpairment_cebcb04d-e122-470f-b973-402d1542c270" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_20f3f43e-03f5-4c80-a0d0-b04cce6a866d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8a60f0f7-bdcd-422f-91ae-b235eb6d6391" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_20f3f43e-03f5-4c80-a0d0-b04cce6a866d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b05c73cc-1c8d-4fd4-87b1-184c016fab22" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_20f3f43e-03f5-4c80-a0d0-b04cce6a866d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b05c73cc-1c8d-4fd4-87b1-184c016fab22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b05c73cc-1c8d-4fd4-87b1-184c016fab22_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b05c73cc-1c8d-4fd4-87b1-184c016fab22" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b05c73cc-1c8d-4fd4-87b1-184c016fab22_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b05c73cc-1c8d-4fd4-87b1-184c016fab22" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_1835b3e1-bdf6-499e-a966-7fbd3d5a8c83" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_1835b3e1-bdf6-499e-a966-7fbd3d5a8c83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_1a089194-4b6a-4bbc-8c43-1a7cd88c54f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:to="loc_us-gaap_CustomerRelationshipsMember_1a089194-4b6a-4bbc-8c43-1a7cd88c54f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_b40eb254-5b6e-4655-adb7-627a08a630d5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:to="loc_us-gaap_CustomerContractsMember_b40eb254-5b6e-4655-adb7-627a08a630d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_15bfd05c-9a4a-40a1-83ef-a57ce1aaeccf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_15bfd05c-9a4a-40a1-83ef-a57ce1aaeccf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_10525146-02ec-4293-9888-65352747440d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_10525146-02ec-4293-9888-65352747440d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_4fac22db-ad27-4610-adb6-559d952ab12c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_30237df4-d1f6-47dd-a945-a53a4eb5cdc8" xlink:to="loc_us-gaap_PatentsMember_4fac22db-ad27-4610-adb6-559d952ab12c" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/EarningsPerShareSharesExcludedfromtheComputationofDilutedNetLossPerShareDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#EarningsPerShareSharesExcludedfromtheComputationofDilutedNetLossPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/EarningsPerShareSharesExcludedfromtheComputationofDilutedNetLossPerShareDetails" xlink:type="extended" id="i0ca8698fe4d94b6ca66ed54e7c613ce7_EarningsPerShareSharesExcludedfromtheComputationofDilutedNetLossPerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_5728cd4d-fba8-4144-b0d0-9fdd8661a4e4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_669d2864-660c-40b6-ab6f-8ec8e11ce4e0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_5728cd4d-fba8-4144-b0d0-9fdd8661a4e4" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_669d2864-660c-40b6-ab6f-8ec8e11ce4e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7f383962-144a-43e0-854a-734dc5d5c5e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_5728cd4d-fba8-4144-b0d0-9fdd8661a4e4" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7f383962-144a-43e0-854a-734dc5d5c5e7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a338d236-b1c4-413b-895f-2f75ad6983f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7f383962-144a-43e0-854a-734dc5d5c5e7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a338d236-b1c4-413b-895f-2f75ad6983f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a338d236-b1c4-413b-895f-2f75ad6983f5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a338d236-b1c4-413b-895f-2f75ad6983f5" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a338d236-b1c4-413b-895f-2f75ad6983f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_587472b8-cbed-4b49-b8be-fcff17ef13fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a338d236-b1c4-413b-895f-2f75ad6983f5" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_587472b8-cbed-4b49-b8be-fcff17ef13fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtSecuritiesMember_8bd928e4-6278-4e31-bc41-3a71f2f2e46d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_587472b8-cbed-4b49-b8be-fcff17ef13fc" xlink:to="loc_us-gaap_ConvertibleDebtSecuritiesMember_8bd928e4-6278-4e31-bc41-3a71f2f2e46d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_41ee025d-21b1-4426-a576-bca8cab24a68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_587472b8-cbed-4b49-b8be-fcff17ef13fc" xlink:to="loc_us-gaap_EmployeeStockOptionMember_41ee025d-21b1-4426-a576-bca8cab24a68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_fece00c9-1074-4007-bf5e-d673d4ef4be0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_587472b8-cbed-4b49-b8be-fcff17ef13fc" xlink:to="loc_us-gaap_WarrantMember_fece00c9-1074-4007-bf5e-d673d4ef4be0" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/StockBasedCompensationStockPlansDetail" xlink:type="simple" xlink:href="smsi-20230331.xsd#StockBasedCompensationStockPlansDetail"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/StockBasedCompensationStockPlansDetail" xlink:type="extended" id="i1ea09490930842dd8ac6e6fd25b84b1a_StockBasedCompensationStockPlansDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_6d633d1d-c0ab-4b5e-97c4-26c3f1a5fb49" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_6d633d1d-c0ab-4b5e-97c4-26c3f1a5fb49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_f6f7d4e4-b2e3-4918-94a3-37e231d2fe68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_f6f7d4e4-b2e3-4918-94a3-37e231d2fe68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_a05d4778-0a64-4085-94fc-453755b89dbd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_a05d4778-0a64-4085-94fc-453755b89dbd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_AwardsSettledInSharesAdjustmentsAgainstShareReserve_3b1d8943-0e7a-420c-b3be-a9585ed3bf30" xlink:href="smsi-20230331.xsd#smsi_AwardsSettledInSharesAdjustmentsAgainstShareReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_smsi_AwardsSettledInSharesAdjustmentsAgainstShareReserve_3b1d8943-0e7a-420c-b3be-a9585ed3bf30" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_af3f58de-e6d1-4d8d-bd2b-ca8e9e5a41a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_af3f58de-e6d1-4d8d-bd2b-ca8e9e5a41a6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePeriodFollowingTermination_d5eaa5f4-3d82-4fbf-ac97-9952f969674a" xlink:href="smsi-20230331.xsd#smsi_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePeriodFollowingTermination"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_smsi_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePeriodFollowingTermination_d5eaa5f4-3d82-4fbf-ac97-9952f969674a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_5220a9c7-076c-45e9-a81e-cfee74152bb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_5220a9c7-076c-45e9-a81e-cfee74152bb6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c31bf9f-f56a-46ab-a96b-83f049d699cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_bcbc9280-938b-4d85-a4f8-9f088170f2a7" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c31bf9f-f56a-46ab-a96b-83f049d699cb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_4918bc6e-2e2d-4c07-b675-f8def1733515" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c31bf9f-f56a-46ab-a96b-83f049d699cb" xlink:to="loc_us-gaap_AwardTypeAxis_4918bc6e-2e2d-4c07-b675-f8def1733515" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4918bc6e-2e2d-4c07-b675-f8def1733515_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_4918bc6e-2e2d-4c07-b675-f8def1733515" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4918bc6e-2e2d-4c07-b675-f8def1733515_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_958909c6-7b89-4295-afc8-e14717fe97c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_4918bc6e-2e2d-4c07-b675-f8def1733515" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_958909c6-7b89-4295-afc8-e14717fe97c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_7305a81e-a50a-4db2-a0e6-1d078acc0f3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_958909c6-7b89-4295-afc8-e14717fe97c5" xlink:to="loc_us-gaap_RestrictedStockMember_7305a81e-a50a-4db2-a0e6-1d078acc0f3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FullValueAwardsMember_da49d3c7-9212-4dd8-9065-c2b51c0bb96b" xlink:href="smsi-20230331.xsd#smsi_FullValueAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_958909c6-7b89-4295-afc8-e14717fe97c5" xlink:to="loc_smsi_FullValueAwardsMember_da49d3c7-9212-4dd8-9065-c2b51c0bb96b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_PartialValueAwardsMember_9eeb45e7-442b-4212-81d9-d7eefe61098a" xlink:href="smsi-20230331.xsd#smsi_PartialValueAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_958909c6-7b89-4295-afc8-e14717fe97c5" xlink:to="loc_smsi_PartialValueAwardsMember_9eeb45e7-442b-4212-81d9-d7eefe61098a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_ba399d70-2063-4149-84d5-4fc3751894cf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c31bf9f-f56a-46ab-a96b-83f049d699cb" xlink:to="loc_us-gaap_PlanNameAxis_ba399d70-2063-4149-84d5-4fc3751894cf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_ba399d70-2063-4149-84d5-4fc3751894cf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_ba399d70-2063-4149-84d5-4fc3751894cf" xlink:to="loc_us-gaap_PlanNameDomain_ba399d70-2063-4149-84d5-4fc3751894cf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_efd85776-3392-4453-ade3-e9d4b8f2a702" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_ba399d70-2063-4149-84d5-4fc3751894cf" xlink:to="loc_us-gaap_PlanNameDomain_efd85776-3392-4453-ade3-e9d4b8f2a702" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_TwoThousandFifteenOmnibusEquityIncentivePlanMember_3147cda8-442d-4120-b056-9b6b9c7123fb" xlink:href="smsi-20230331.xsd#smsi_TwoThousandFifteenOmnibusEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_efd85776-3392-4453-ade3-e9d4b8f2a702" xlink:to="loc_smsi_TwoThousandFifteenOmnibusEquityIncentivePlanMember_3147cda8-442d-4120-b056-9b6b9c7123fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_07b98dac-f780-44ea-a226-a9c06595617e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0c31bf9f-f56a-46ab-a96b-83f049d699cb" xlink:to="loc_srt_RangeAxis_07b98dac-f780-44ea-a226-a9c06595617e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_07b98dac-f780-44ea-a226-a9c06595617e_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_07b98dac-f780-44ea-a226-a9c06595617e" xlink:to="loc_srt_RangeMember_07b98dac-f780-44ea-a226-a9c06595617e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5869f486-d001-4806-89b2-fc8e280255ba" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_07b98dac-f780-44ea-a226-a9c06595617e" xlink:to="loc_srt_RangeMember_5869f486-d001-4806-89b2-fc8e280255ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_4f9e6bb9-514d-4352-b089-016ccaf574c9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5869f486-d001-4806-89b2-fc8e280255ba" xlink:to="loc_srt_MaximumMember_4f9e6bb9-514d-4352-b089-016ccaf574c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_84e83941-66b4-4630-80f8-8e4e3ea257b4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5869f486-d001-4806-89b2-fc8e280255ba" xlink:to="loc_srt_MinimumMember_84e83941-66b4-4630-80f8-8e4e3ea257b4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/StockBasedCompensationEmployeeStockPurchasePlanDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#StockBasedCompensationEmployeeStockPurchasePlanDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/StockBasedCompensationEmployeeStockPurchasePlanDetails" xlink:type="extended" id="i68599d0518c648a39003dc854dab274c_StockBasedCompensationEmployeeStockPurchasePlanDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_27e0b4cb-cd8c-47eb-94b5-aeb77cc522f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_PercentageOfFairMarketValueOfShare_61e8a07d-d981-40fe-b909-46fe02fd78ce" xlink:href="smsi-20230331.xsd#smsi_PercentageOfFairMarketValueOfShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_27e0b4cb-cd8c-47eb-94b5-aeb77cc522f5" xlink:to="loc_smsi_PercentageOfFairMarketValueOfShare_61e8a07d-d981-40fe-b909-46fe02fd78ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_PercentageOfEmployeeCompensationForEmployeePayrollDeduction_99dc84e4-cd95-489c-8698-dc254647297a" xlink:href="smsi-20230331.xsd#smsi_PercentageOfEmployeeCompensationForEmployeePayrollDeduction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_27e0b4cb-cd8c-47eb-94b5-aeb77cc522f5" xlink:to="loc_smsi_PercentageOfEmployeeCompensationForEmployeePayrollDeduction_99dc84e4-cd95-489c-8698-dc254647297a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_MaximumStockValueOfSharesPurchasedByEmployees_842d3f06-b3eb-40e0-a2fa-6701a1f342d0" xlink:href="smsi-20230331.xsd#smsi_MaximumStockValueOfSharesPurchasedByEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_27e0b4cb-cd8c-47eb-94b5-aeb77cc522f5" xlink:to="loc_smsi_MaximumStockValueOfSharesPurchasedByEmployees_842d3f06-b3eb-40e0-a2fa-6701a1f342d0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_MaximumSharesPurchasedByEmployees_f1840526-9f42-46c7-9c2a-4860bdb96091" xlink:href="smsi-20230331.xsd#smsi_MaximumSharesPurchasedByEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_27e0b4cb-cd8c-47eb-94b5-aeb77cc522f5" xlink:to="loc_smsi_MaximumSharesPurchasedByEmployees_f1840526-9f42-46c7-9c2a-4860bdb96091" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_18fe2f8c-48ac-462b-91b1-6b03688c4337" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_27e0b4cb-cd8c-47eb-94b5-aeb77cc522f5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_18fe2f8c-48ac-462b-91b1-6b03688c4337" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4b4e1539-a021-47ca-aa92-0f1307bb9b97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_27e0b4cb-cd8c-47eb-94b5-aeb77cc522f5" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4b4e1539-a021-47ca-aa92-0f1307bb9b97" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_9b8ada28-c976-44c2-a988-64a683446cdd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4b4e1539-a021-47ca-aa92-0f1307bb9b97" xlink:to="loc_us-gaap_AwardTypeAxis_9b8ada28-c976-44c2-a988-64a683446cdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9b8ada28-c976-44c2-a988-64a683446cdd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_9b8ada28-c976-44c2-a988-64a683446cdd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9b8ada28-c976-44c2-a988-64a683446cdd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_740473f5-af0f-422c-a3eb-004ce565c8e5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_9b8ada28-c976-44c2-a988-64a683446cdd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_740473f5-af0f-422c-a3eb-004ce565c8e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_EmployeeStockPurchasePlanMember_ce97aa78-53c1-4528-9b34-7fa3dce589e0" xlink:href="smsi-20230331.xsd#smsi_EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_740473f5-af0f-422c-a3eb-004ce565c8e5" xlink:to="loc_smsi_EmployeeStockPurchasePlanMember_ce97aa78-53c1-4528-9b34-7fa3dce589e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_acd238ac-e562-44e5-b89e-3ab75b0be041" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4b4e1539-a021-47ca-aa92-0f1307bb9b97" xlink:to="loc_srt_RangeAxis_acd238ac-e562-44e5-b89e-3ab75b0be041" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_acd238ac-e562-44e5-b89e-3ab75b0be041_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_acd238ac-e562-44e5-b89e-3ab75b0be041" xlink:to="loc_srt_RangeMember_acd238ac-e562-44e5-b89e-3ab75b0be041_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c05c7ef6-c3e5-4317-a2c3-3b40f7d3d393" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_acd238ac-e562-44e5-b89e-3ab75b0be041" xlink:to="loc_srt_RangeMember_c05c7ef6-c3e5-4317-a2c3-3b40f7d3d393" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ffa94a9a-03f3-4087-b5c5-647bc4d58f4f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c05c7ef6-c3e5-4317-a2c3-3b40f7d3d393" xlink:to="loc_srt_MaximumMember_ffa94a9a-03f3-4087-b5c5-647bc4d58f4f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/StockBasedCompensationNoncashstockbasedcompensationexpenseDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#StockBasedCompensationNoncashstockbasedcompensationexpenseDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/StockBasedCompensationNoncashstockbasedcompensationexpenseDetails" xlink:type="extended" id="iee9c6b60816a4c27803631abef7ea395_StockBasedCompensationNoncashstockbasedcompensationexpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5706838d-07b1-40ef-9061-498790203bac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_bc556089-7c5c-4221-b04b-7071ce01866e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5706838d-07b1-40ef-9061-498790203bac" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_bc556089-7c5c-4221-b04b-7071ce01866e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_32f8f118-5871-4043-a5f0-c6b7da36aea8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5706838d-07b1-40ef-9061-498790203bac" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_32f8f118-5871-4043-a5f0-c6b7da36aea8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_971aaef5-cae4-46d9-af23-24669a798ad4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5706838d-07b1-40ef-9061-498790203bac" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_971aaef5-cae4-46d9-af23-24669a798ad4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_9a6f8a6c-b392-4b1d-8ae1-16972f45dff9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_971aaef5-cae4-46d9-af23-24669a798ad4" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_9a6f8a6c-b392-4b1d-8ae1-16972f45dff9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9a6f8a6c-b392-4b1d-8ae1-16972f45dff9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_9a6f8a6c-b392-4b1d-8ae1-16972f45dff9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9a6f8a6c-b392-4b1d-8ae1-16972f45dff9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_fd31e2e1-bbe1-48d3-874a-f40a342d7543" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_9a6f8a6c-b392-4b1d-8ae1-16972f45dff9" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_fd31e2e1-bbe1-48d3-874a-f40a342d7543" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_SalesAndMarketingExpenseMember_3d9dd4d1-8757-4378-b34a-a0cdaced9bcb" xlink:href="smsi-20230331.xsd#smsi_SalesAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fd31e2e1-bbe1-48d3-874a-f40a342d7543" xlink:to="loc_smsi_SalesAndMarketingExpenseMember_3d9dd4d1-8757-4378-b34a-a0cdaced9bcb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_8ab0fff8-0ed0-4931-8e3e-43f9dfdfae89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fd31e2e1-bbe1-48d3-874a-f40a342d7543" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_8ab0fff8-0ed0-4931-8e3e-43f9dfdfae89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_89fd1a12-996a-4afc-a297-8c726cd20aab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fd31e2e1-bbe1-48d3-874a-f40a342d7543" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_89fd1a12-996a-4afc-a297-8c726cd20aab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_0781b46e-545c-4284-822b-565b302e5ca6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_971aaef5-cae4-46d9-af23-24669a798ad4" xlink:to="loc_us-gaap_AwardTypeAxis_0781b46e-545c-4284-822b-565b302e5ca6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0781b46e-545c-4284-822b-565b302e5ca6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_0781b46e-545c-4284-822b-565b302e5ca6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0781b46e-545c-4284-822b-565b302e5ca6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c2412026-75b0-479f-be96-78b7361f48f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_0781b46e-545c-4284-822b-565b302e5ca6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c2412026-75b0-479f-be96-78b7361f48f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_af252f81-867b-4e4a-8bbb-66d35cf54558" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c2412026-75b0-479f-be96-78b7361f48f8" xlink:to="loc_us-gaap_RestrictedStockMember_af252f81-867b-4e4a-8bbb-66d35cf54558" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/StockBasedCompensationSummaryofrestrictedstockawardsoutstandingDetails" xlink:type="simple" xlink:href="smsi-20230331.xsd#StockBasedCompensationSummaryofrestrictedstockawardsoutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/StockBasedCompensationSummaryofrestrictedstockawardsoutstandingDetails" xlink:type="extended" id="i6651c5709ad34ebe988c969397b7dae2_StockBasedCompensationSummaryofrestrictedstockawardsoutstandingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39eb180e-e340-487f-a63a-961676d51a0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_8c01386f-2696-4242-a7a4-874cf3156b88" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39eb180e-e340-487f-a63a-961676d51a0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_8c01386f-2696-4242-a7a4-874cf3156b88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_73a64d4b-8870-4ac6-9300-a656e12264f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_8c01386f-2696-4242-a7a4-874cf3156b88" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_73a64d4b-8870-4ac6-9300-a656e12264f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0a9e41e8-454e-428c-82af-75fa0bb4f20d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_8c01386f-2696-4242-a7a4-874cf3156b88" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0a9e41e8-454e-428c-82af-75fa0bb4f20d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_a53e61e4-3a76-414d-a762-0c4cfc8e21a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_8c01386f-2696-4242-a7a4-874cf3156b88" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_a53e61e4-3a76-414d-a762-0c4cfc8e21a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_406ec2f5-e070-4a58-a3f2-d11f9d9002ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_8c01386f-2696-4242-a7a4-874cf3156b88" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_406ec2f5-e070-4a58-a3f2-d11f9d9002ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_351059b7-169e-42dd-9a1e-e1cc8485d698" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_4a5b44f0-9565-4afb-b602-068bdb32bb3e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39eb180e-e340-487f-a63a-961676d51a0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_4a5b44f0-9565-4afb-b602-068bdb32bb3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_71a069f3-640f-49b3-9b6a-8f19129f54a4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_4a5b44f0-9565-4afb-b602-068bdb32bb3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_71a069f3-640f-49b3-9b6a-8f19129f54a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_a121a69f-651e-49c3-a678-7e2c9c30b3a7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_4a5b44f0-9565-4afb-b602-068bdb32bb3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_a121a69f-651e-49c3-a678-7e2c9c30b3a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_39cf1f96-e9fb-4a2c-bc5f-1971ae0dafe9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_4a5b44f0-9565-4afb-b602-068bdb32bb3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_39cf1f96-e9fb-4a2c-bc5f-1971ae0dafe9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_f5f3d82b-0aff-406b-8df4-7a5a8871613b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_4a5b44f0-9565-4afb-b602-068bdb32bb3e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_f5f3d82b-0aff-406b-8df4-7a5a8871613b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_8ab8a9bb-9d61-42f6-917a-f2f6cee8da22" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4edb9929-b59d-40f6-af38-b3784111f49d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_39eb180e-e340-487f-a63a-961676d51a0e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4edb9929-b59d-40f6-af38-b3784111f49d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_2d1b4c5c-482c-4b19-939f-68c01a2313a4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4edb9929-b59d-40f6-af38-b3784111f49d" xlink:to="loc_us-gaap_AwardTypeAxis_2d1b4c5c-482c-4b19-939f-68c01a2313a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2d1b4c5c-482c-4b19-939f-68c01a2313a4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_2d1b4c5c-482c-4b19-939f-68c01a2313a4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2d1b4c5c-482c-4b19-939f-68c01a2313a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4839180b-eb15-4bec-8ee5-2801481f9ae2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_2d1b4c5c-482c-4b19-939f-68c01a2313a4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4839180b-eb15-4bec-8ee5-2801481f9ae2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_fe1edd1c-3cd9-49bd-81b0-8d377aa75c5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4839180b-eb15-4bec-8ee5-2801481f9ae2" xlink:to="loc_us-gaap_RestrictedStockMember_fe1edd1c-3cd9-49bd-81b0-8d377aa75c5b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/RevenuesScheduleofRevenuesonDisaggregatedBasisDetail" xlink:type="simple" xlink:href="smsi-20230331.xsd#RevenuesScheduleofRevenuesonDisaggregatedBasisDetail"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/RevenuesScheduleofRevenuesonDisaggregatedBasisDetail" xlink:type="extended" id="i6ee8f7cb23434df4bc0291dbb9c27edf_RevenuesScheduleofRevenuesonDisaggregatedBasisDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_fef95441-4152-4244-b82a-332bdb1069bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b9eecb6f-9067-4743-af3c-c41e13061068" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_fef95441-4152-4244-b82a-332bdb1069bd" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b9eecb6f-9067-4743-af3c-c41e13061068" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_f3fae6a2-6221-459b-8c01-7840631f9c40" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_fef95441-4152-4244-b82a-332bdb1069bd" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_f3fae6a2-6221-459b-8c01-7840631f9c40" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_f974b223-046a-483b-8bba-687d00e73249" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f3fae6a2-6221-459b-8c01-7840631f9c40" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_f974b223-046a-483b-8bba-687d00e73249" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f974b223-046a-483b-8bba-687d00e73249_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_f974b223-046a-483b-8bba-687d00e73249" xlink:to="loc_us-gaap_SegmentDomain_f974b223-046a-483b-8bba-687d00e73249_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_744ee11c-cfaa-4a57-90c5-59ae13dced4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_f974b223-046a-483b-8bba-687d00e73249" xlink:to="loc_us-gaap_SegmentDomain_744ee11c-cfaa-4a57-90c5-59ae13dced4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_WirelessBusinessSegmentMember_5d45b18d-e3e1-474e-b74f-99e021ac4730" xlink:href="smsi-20230331.xsd#smsi_WirelessBusinessSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_744ee11c-cfaa-4a57-90c5-59ae13dced4f" xlink:to="loc_smsi_WirelessBusinessSegmentMember_5d45b18d-e3e1-474e-b74f-99e021ac4730" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_b4de812e-6bb9-48de-a096-09e4b189d22f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f3fae6a2-6221-459b-8c01-7840631f9c40" xlink:to="loc_srt_ProductOrServiceAxis_b4de812e-6bb9-48de-a096-09e4b189d22f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_b4de812e-6bb9-48de-a096-09e4b189d22f_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_b4de812e-6bb9-48de-a096-09e4b189d22f" xlink:to="loc_srt_ProductsAndServicesDomain_b4de812e-6bb9-48de-a096-09e4b189d22f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_2ddb3807-15c2-4830-afca-d2de489468f1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_b4de812e-6bb9-48de-a096-09e4b189d22f" xlink:to="loc_srt_ProductsAndServicesDomain_2ddb3807-15c2-4830-afca-d2de489468f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicenseAndServiceMember_70778a64-06b7-404e-b278-8e99ed8fbc67" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LicenseAndServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2ddb3807-15c2-4830-afca-d2de489468f1" xlink:to="loc_us-gaap_LicenseAndServiceMember_70778a64-06b7-404e-b278-8e99ed8fbc67" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_HostedEnvironmentUsageFeesMember_872ed823-3768-48db-b5d9-b3b0419ba246" xlink:href="smsi-20230331.xsd#smsi_HostedEnvironmentUsageFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2ddb3807-15c2-4830-afca-d2de489468f1" xlink:to="loc_smsi_HostedEnvironmentUsageFeesMember_872ed823-3768-48db-b5d9-b3b0419ba246" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_CloudBasedUsageFeesMember_a696e0f1-5f1c-491c-9ebe-dd2f2564b128" xlink:href="smsi-20230331.xsd#smsi_CloudBasedUsageFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2ddb3807-15c2-4830-afca-d2de489468f1" xlink:to="loc_smsi_CloudBasedUsageFeesMember_a696e0f1-5f1c-491c-9ebe-dd2f2564b128" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_ConsultingServicesAndOtherMember_5e9a0a7f-655f-4cfe-aa47-02beeffe13f6" xlink:href="smsi-20230331.xsd#smsi_ConsultingServicesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2ddb3807-15c2-4830-afca-d2de489468f1" xlink:to="loc_smsi_ConsultingServicesAndOtherMember_5e9a0a7f-655f-4cfe-aa47-02beeffe13f6" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/SegmentCustomerConcentrationandGeographicalInformationAdditionalInformationDetail" xlink:type="simple" xlink:href="smsi-20230331.xsd#SegmentCustomerConcentrationandGeographicalInformationAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/SegmentCustomerConcentrationandGeographicalInformationAdditionalInformationDetail" xlink:type="extended" id="ib365d2bb713a4de6b7faf97d41e5a440_SegmentCustomerConcentrationandGeographicalInformationAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a641ce4-936d-47d4-828b-c1193014e5dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EntityWideRevenueMajorCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_065914a9-b4c8-49c6-9502-96e39b2f89be" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a641ce4-936d-47d4-828b-c1193014e5dc" xlink:to="loc_us-gaap_NumberOfOperatingSegments_065914a9-b4c8-49c6-9502-96e39b2f89be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_4427f78e-fa1d-4061-961e-c0c4f800d8e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a641ce4-936d-47d4-828b-c1193014e5dc" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_4427f78e-fa1d-4061-961e-c0c4f800d8e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_NumberOfGeographicLocation_e441d378-0a67-47da-880e-aba77c7c60cd" xlink:href="smsi-20230331.xsd#smsi_NumberOfGeographicLocation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a641ce4-936d-47d4-828b-c1193014e5dc" xlink:to="loc_smsi_NumberOfGeographicLocation_e441d378-0a67-47da-880e-aba77c7c60cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_03c60709-5f05-4133-9e76-336989aaf14a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a641ce4-936d-47d4-828b-c1193014e5dc" xlink:to="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_03c60709-5f05-4133-9e76-336989aaf14a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_4c6db1a8-2f7f-4a07-992b-22b84905eb7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_03c60709-5f05-4133-9e76-336989aaf14a" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_4c6db1a8-2f7f-4a07-992b-22b84905eb7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_4c6db1a8-2f7f-4a07-992b-22b84905eb7a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_4c6db1a8-2f7f-4a07-992b-22b84905eb7a" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_4c6db1a8-2f7f-4a07-992b-22b84905eb7a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_fcc32bd8-92a1-4ba7-90f0-fa2eacc4ed63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_4c6db1a8-2f7f-4a07-992b-22b84905eb7a" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_fcc32bd8-92a1-4ba7-90f0-fa2eacc4ed63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_d88f0484-8ca3-42d3-94d9-9b3a82facac8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_fcc32bd8-92a1-4ba7-90f0-fa2eacc4ed63" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_d88f0484-8ca3-42d3-94d9-9b3a82facac8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_84e918be-80be-4e07-94da-86d24d12af1b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_03c60709-5f05-4133-9e76-336989aaf14a" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_84e918be-80be-4e07-94da-86d24d12af1b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_84e918be-80be-4e07-94da-86d24d12af1b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_84e918be-80be-4e07-94da-86d24d12af1b" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_84e918be-80be-4e07-94da-86d24d12af1b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_44d0e535-21d0-4925-986f-948893225a26" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_84e918be-80be-4e07-94da-86d24d12af1b" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_44d0e535-21d0-4925-986f-948893225a26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_ec9d3ab8-6e40-426c-82b5-0b127733c3e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_44d0e535-21d0-4925-986f-948893225a26" xlink:to="loc_us-gaap_SalesRevenueNetMember_ec9d3ab8-6e40-426c-82b5-0b127733c3e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_50901bdc-6839-4d8c-b24a-32b6dc9ae24a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_44d0e535-21d0-4925-986f-948893225a26" xlink:to="loc_us-gaap_AccountsReceivableMember_50901bdc-6839-4d8c-b24a-32b6dc9ae24a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_82822d74-1b95-4fb4-857a-93b777ef2ec4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_03c60709-5f05-4133-9e76-336989aaf14a" xlink:to="loc_srt_MajorCustomersAxis_82822d74-1b95-4fb4-857a-93b777ef2ec4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_82822d74-1b95-4fb4-857a-93b777ef2ec4_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_82822d74-1b95-4fb4-857a-93b777ef2ec4" xlink:to="loc_srt_NameOfMajorCustomerDomain_82822d74-1b95-4fb4-857a-93b777ef2ec4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_19a8aa39-7b29-4320-a8ab-23049935c20e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_82822d74-1b95-4fb4-857a-93b777ef2ec4" xlink:to="loc_srt_NameOfMajorCustomerDomain_19a8aa39-7b29-4320-a8ab-23049935c20e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_OneCustomersMember_52294f0a-6d76-434e-9f6c-6f6483407755" xlink:href="smsi-20230331.xsd#smsi_OneCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_19a8aa39-7b29-4320-a8ab-23049935c20e" xlink:to="loc_smsi_OneCustomersMember_52294f0a-6d76-434e-9f6c-6f6483407755" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_TwoCustomerMember_d81ea578-22f3-4314-a99f-955a8db9fa9a" xlink:href="smsi-20230331.xsd#smsi_TwoCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_19a8aa39-7b29-4320-a8ab-23049935c20e" xlink:to="loc_smsi_TwoCustomerMember_d81ea578-22f3-4314-a99f-955a8db9fa9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_ThreeCustomerMember_196f2ff6-ff6c-4f25-b188-c9ac11f6630e" xlink:href="smsi-20230331.xsd#smsi_ThreeCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_19a8aa39-7b29-4320-a8ab-23049935c20e" xlink:to="loc_smsi_ThreeCustomerMember_196f2ff6-ff6c-4f25-b188-c9ac11f6630e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_CustomerFourMember_f522269f-b6cb-45cd-88a0-987432216879" xlink:href="smsi-20230331.xsd#smsi_CustomerFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_19a8aa39-7b29-4320-a8ab-23049935c20e" xlink:to="loc_smsi_CustomerFourMember_f522269f-b6cb-45cd-88a0-987432216879" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/SegmentCustomerConcentrationandGeographicalInformationWirelessRevenuesbyProductDetail" xlink:type="simple" xlink:href="smsi-20230331.xsd#SegmentCustomerConcentrationandGeographicalInformationWirelessRevenuesbyProductDetail"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/SegmentCustomerConcentrationandGeographicalInformationWirelessRevenuesbyProductDetail" xlink:type="extended" id="i16217b183069425d93a52a3657f47973_SegmentCustomerConcentrationandGeographicalInformationWirelessRevenuesbyProductDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_2536ea65-e9cb-41f8-a8fa-3c7439cb380a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c5748637-f79f-4ba3-9541-dc4665f32dbd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_2536ea65-e9cb-41f8-a8fa-3c7439cb380a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c5748637-f79f-4ba3-9541-dc4665f32dbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_33514ad4-6e9f-4b97-b579-a13cceb331ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_2536ea65-e9cb-41f8-a8fa-3c7439cb380a" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_33514ad4-6e9f-4b97-b579-a13cceb331ed" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_8f78f3b2-d543-4459-9e3f-38621b5bd6d4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_33514ad4-6e9f-4b97-b579-a13cceb331ed" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_8f78f3b2-d543-4459-9e3f-38621b5bd6d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_8f78f3b2-d543-4459-9e3f-38621b5bd6d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8f78f3b2-d543-4459-9e3f-38621b5bd6d4" xlink:to="loc_us-gaap_SegmentDomain_8f78f3b2-d543-4459-9e3f-38621b5bd6d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_30fea8d7-bcbb-4fa9-b48f-9c6ef86da658" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8f78f3b2-d543-4459-9e3f-38621b5bd6d4" xlink:to="loc_us-gaap_SegmentDomain_30fea8d7-bcbb-4fa9-b48f-9c6ef86da658" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_WirelessBusinessSegmentMember_973ca0bb-343e-4583-85b5-c8c6b6c9e90d" xlink:href="smsi-20230331.xsd#smsi_WirelessBusinessSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_30fea8d7-bcbb-4fa9-b48f-9c6ef86da658" xlink:to="loc_smsi_WirelessBusinessSegmentMember_973ca0bb-343e-4583-85b5-c8c6b6c9e90d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_5cba88ac-da5c-4689-9458-8e0ee33bbdf0" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_33514ad4-6e9f-4b97-b579-a13cceb331ed" xlink:to="loc_srt_ProductOrServiceAxis_5cba88ac-da5c-4689-9458-8e0ee33bbdf0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_5cba88ac-da5c-4689-9458-8e0ee33bbdf0_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_5cba88ac-da5c-4689-9458-8e0ee33bbdf0" xlink:to="loc_srt_ProductsAndServicesDomain_5cba88ac-da5c-4689-9458-8e0ee33bbdf0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_3c1a62dd-37a2-4db4-a783-8861dd693368" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_5cba88ac-da5c-4689-9458-8e0ee33bbdf0" xlink:to="loc_srt_ProductsAndServicesDomain_3c1a62dd-37a2-4db4-a783-8861dd693368" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_FamilySafetyMember_a33a33d9-e57d-4a6e-ac59-d7dc4960fc64" xlink:href="smsi-20230331.xsd#smsi_FamilySafetyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_3c1a62dd-37a2-4db4-a783-8861dd693368" xlink:to="loc_smsi_FamilySafetyMember_a33a33d9-e57d-4a6e-ac59-d7dc4960fc64" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_CommSuiteMember_e7ed6744-6b73-48a5-82bc-658362bee6fe" xlink:href="smsi-20230331.xsd#smsi_CommSuiteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_3c1a62dd-37a2-4db4-a783-8861dd693368" xlink:to="loc_smsi_CommSuiteMember_e7ed6744-6b73-48a5-82bc-658362bee6fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smsi_ViewSpotMember_ebc567bd-d4f9-422e-ae3d-aa3709e37f4a" xlink:href="smsi-20230331.xsd#smsi_ViewSpotMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_3c1a62dd-37a2-4db4-a783-8861dd693368" xlink:to="loc_smsi_ViewSpotMember_ebc567bd-d4f9-422e-ae3d-aa3709e37f4a" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.smithmicro.com/role/SegmentCustomerConcentrationandGeographicalInformationCompanyRevenueinDifferentGeographicLocationsDetail" xlink:type="simple" xlink:href="smsi-20230331.xsd#SegmentCustomerConcentrationandGeographicalInformationCompanyRevenueinDifferentGeographicLocationsDetail"/>
  <link:definitionLink xlink:role="http://www.smithmicro.com/role/SegmentCustomerConcentrationandGeographicalInformationCompanyRevenueinDifferentGeographicLocationsDetail" xlink:type="extended" id="i8284ec479b8d42d7b22ae93740460069_SegmentCustomerConcentrationandGeographicalInformationCompanyRevenueinDifferentGeographicLocationsDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_c9a152ac-0dcd-4015-8a16-acbabe3937a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_35ef9c7c-4a78-4360-aa1f-6d7368a27166" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_c9a152ac-0dcd-4015-8a16-acbabe3937a2" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_35ef9c7c-4a78-4360-aa1f-6d7368a27166" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_b4368ce9-48df-40b5-aed9-944f084c8804" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_c9a152ac-0dcd-4015-8a16-acbabe3937a2" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_b4368ce9-48df-40b5-aed9-944f084c8804" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_7829831f-d22f-4225-a62b-43660262057e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_b4368ce9-48df-40b5-aed9-944f084c8804" xlink:to="loc_srt_StatementGeographicalAxis_7829831f-d22f-4225-a62b-43660262057e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_7829831f-d22f-4225-a62b-43660262057e_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_7829831f-d22f-4225-a62b-43660262057e" xlink:to="loc_srt_SegmentGeographicalDomain_7829831f-d22f-4225-a62b-43660262057e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_08f45f6d-6de3-4fd2-bfd6-b99a5809a7bb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_7829831f-d22f-4225-a62b-43660262057e" xlink:to="loc_srt_SegmentGeographicalDomain_08f45f6d-6de3-4fd2-bfd6-b99a5809a7bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AmericasMember_43859d6d-af99-4515-884b-4a21b9df50aa" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AmericasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_08f45f6d-6de3-4fd2-bfd6-b99a5809a7bb" xlink:to="loc_srt_AmericasMember_43859d6d-af99-4515-884b-4a21b9df50aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_6ba645cc-4d51-41fb-aa78-988ed17a98a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_08f45f6d-6de3-4fd2-bfd6-b99a5809a7bb" xlink:to="loc_us-gaap_EMEAMember_6ba645cc-4d51-41fb-aa78-988ed17a98a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_9ff05da2-24a2-44db-93eb-6df018ec0fa7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_b4368ce9-48df-40b5-aed9-944f084c8804" xlink:to="loc_srt_ConsolidationItemsAxis_9ff05da2-24a2-44db-93eb-6df018ec0fa7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_9ff05da2-24a2-44db-93eb-6df018ec0fa7_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_9ff05da2-24a2-44db-93eb-6df018ec0fa7" xlink:to="loc_srt_ConsolidationItemsDomain_9ff05da2-24a2-44db-93eb-6df018ec0fa7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_fc93c324-6b42-4195-9674-67378a176152" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_9ff05da2-24a2-44db-93eb-6df018ec0fa7" xlink:to="loc_srt_ConsolidationItemsDomain_fc93c324-6b42-4195-9674-67378a176152" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ReportableGeographicalComponentsMember_397b40e0-88af-4d9c-b58a-39ea0adab3b3" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ReportableGeographicalComponentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_fc93c324-6b42-4195-9674-67378a176152" xlink:to="loc_srt_ReportableGeographicalComponentsMember_397b40e0-88af-4d9c-b58a-39ea0adab3b3" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
