<?xml version="1.0" encoding="utf-8"?>
<!--Generated by DFIN XBRL Instance Document - http://www.dfinsolutions.com/ - Version R3.0 - on 09-May-2025 [04:41:02] {AM}-->
<linkbase xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:xbrldt="http://xbrl.org/2005/xbrldt">
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#CoverPage" roleURI="http://cslm.com/role/CoverPage" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#ConsolidatedBalanceSheets" roleURI="http://cslm.com/role/ConsolidatedBalanceSheets" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#ConsolidatedBalanceSheetsParenthetical" roleURI="http://cslm.com/role/ConsolidatedBalanceSheetsParenthetical" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#ConsolidatedStatementsOfOperations" roleURI="http://cslm.com/role/ConsolidatedStatementsOfOperations" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#ConsolidatedStatementsOfChangesInClassAOrdinarySharesSubjectToPossibleRedemptionAndShareholdersDeficit" roleURI="http://cslm.com/role/ConsolidatedStatementsOfChangesInClassAOrdinarySharesSubjectToPossibleRedemptionAndShareholdersDeficit" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#OrganizationAndBusinessBackgroundAdditionalInformationDetail" roleURI="http://cslm.com/role/OrganizationAndBusinessBackgroundAdditionalInformationDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" roleURI="http://cslm.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#SummaryOfSignificantAccountingPoliciesSummaryOfEarningsPerShareBasicAndDilutedDetail" roleURI="http://cslm.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfEarningsPerShareBasicAndDilutedDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#InitialPublicOfferingAdditionalInformationDetail" roleURI="http://cslm.com/role/InitialPublicOfferingAdditionalInformationDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#PrivatePlacementAddtionalInformationDetail" roleURI="http://cslm.com/role/PrivatePlacementAddtionalInformationDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#RelatedPartyTransactionsAdditionalInformationDetail" roleURI="http://cslm.com/role/RelatedPartyTransactionsAdditionalInformationDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#ShareholdersDeficitAdditionalInformationDetail" roleURI="http://cslm.com/role/ShareholdersDeficitAdditionalInformationDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#CommitmentsAndContingenciesAdditionalInformationDetail" roleURI="http://cslm.com/role/CommitmentsAndContingenciesAdditionalInformationDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#FairValueMeasurementsSummaryOfTheFairValueHierarchyTheCompanySAssetsAndLiabilitiesThatWereAccountedForAtFairValueOnARecurringBasisDetail" roleURI="http://cslm.com/role/FairValueMeasurementsSummaryOfTheFairValueHierarchyTheCompanySAssetsAndLiabilitiesThatWereAccountedForAtFairValueOnARecurringBasisDetail" />
<roleRef xlink:type="simple" xlink:href="fuse-20241231.xsd#SubsequentEventsAdditionalInformationDetail" roleURI="http://cslm.com/role/SubsequentEventsAdditionalInformationDetail" />
<arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" />
<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" />
<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" />
<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" />
<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" />
<arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/notAll" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#notAll" />
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/CoverPage">
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentInformationLineItems" xlink:label="loc_dei_DocumentInformationLineItems_1419388" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentInformationTable" xlink:label="loc_dei_DocumentInformationTable_1419362" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_DocumentInformationTable_1419362" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419386" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_1419362" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419386" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419387" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419386" xlink:to="loc_us-gaap_ClassOfStockDomain_1419387" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419387_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419386" xlink:to="loc_us-gaap_ClassOfStockDomain_1419387_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_1420153" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_1419362" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_1420153" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_1420156" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1420153" xlink:to="loc_us-gaap_EquityComponentDomain_1420156" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_1420156_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1420153" xlink:to="loc_us-gaap_EquityComponentDomain_1420156_default" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressesAddressTypeAxis" xlink:label="loc_dei_EntityAddressesAddressTypeAxis_1707052" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_1419362" xlink:to="loc_dei_EntityAddressesAddressTypeAxis_1707052" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AddressTypeDomain" xlink:label="loc_dei_AddressTypeDomain_1707053" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_EntityAddressesAddressTypeAxis_1707052" xlink:to="loc_dei_AddressTypeDomain_1707053" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AddressTypeDomain" xlink:label="loc_dei_AddressTypeDomain_1707053_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_EntityAddressesAddressTypeAxis_1707052" xlink:to="loc_dei_AddressTypeDomain_1707053_default" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_BusinessContactMember" xlink:label="loc_dei_BusinessContactMember_1707054" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_AddressTypeDomain_1707053" xlink:to="loc_dei_BusinessContactMember_1707054" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentType" xlink:label="loc_dei_DocumentType_1419389" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_DocumentType_1419389" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AmendmentFlag" xlink:label="loc_dei_AmendmentFlag_1419391" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_AmendmentFlag_1419391" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AmendmentDescription" xlink:label="loc_dei_AmendmentDescription_1707149" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_AmendmentDescription_1707149" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityRegistrantName" xlink:label="loc_dei_EntityRegistrantName_1419396" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityRegistrantName_1419396" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCentralIndexKey" xlink:label="loc_dei_EntityCentralIndexKey_1419397" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityCentralIndexKey_1419397" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityTaxIdentificationNumber" xlink:label="loc_dei_EntityTaxIdentificationNumber_1419400" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityTaxIdentificationNumber_1419400" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityIncorporationStateCountryCode" xlink:label="loc_dei_EntityIncorporationStateCountryCode_1419401" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityIncorporationStateCountryCode_1419401" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFilerCategory" xlink:label="loc_dei_EntityFilerCategory_1419406" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityFilerCategory_1419406" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntitySmallBusiness" xlink:label="loc_dei_EntitySmallBusiness_1419407" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntitySmallBusiness_1419407" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityEmergingGrowthCompany" xlink:label="loc_dei_EntityEmergingGrowthCompany_1419408" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityEmergingGrowthCompany_1419408" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityExTransitionPeriod" xlink:label="loc_dei_EntityExTransitionPeriod_1419409" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityExTransitionPeriod_1419409" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine1" xlink:label="loc_dei_EntityAddressAddressLine1_1419410" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityAddressAddressLine1_1419410" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine2" xlink:label="loc_dei_EntityAddressAddressLine2_1419411" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityAddressAddressLine2_1419411" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressCityOrTown" xlink:label="loc_dei_EntityAddressCityOrTown_1419412" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityAddressCityOrTown_1419412" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressStateOrProvince" xlink:label="loc_dei_EntityAddressStateOrProvince_1419413" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityAddressStateOrProvince_1419413" use="optional" order="26" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressPostalZipCode" xlink:label="loc_dei_EntityAddressPostalZipCode_1419414" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityAddressPostalZipCode_1419414" use="optional" order="27" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CityAreaCode" xlink:label="loc_dei_CityAreaCode_1419415" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_CityAreaCode_1419415" use="optional" order="28" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_LocalPhoneNumber" xlink:label="loc_dei_LocalPhoneNumber_1419416" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_LocalPhoneNumber_1419416" use="optional" order="29" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_ContactPersonnelName" xlink:label="loc_dei_ContactPersonnelName_1707055" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_ContactPersonnelName_1707055" use="optional" order="30" />
<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityPrimarySicNumber" xlink:label="loc_dei_EntityPrimarySicNumber_1707150" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_1419388" xlink:to="loc_dei_EntityPrimarySicNumber_1707150" use="optional" order="31" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/ConsolidatedBalanceSheets">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1419003" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1419000" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1419003" xlink:to="loc_us-gaap_StatementTable_1419000" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1706746" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419000" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1706746" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1706747" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1706746" xlink:to="loc_us-gaap_ClassOfStockDomain_1706747" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1706747_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1706746" xlink:to="loc_us-gaap_ClassOfStockDomain_1706747_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1419004" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1706747" xlink:to="loc_us-gaap_CommonClassAMember_1419004" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaap_CommonClassBMember_1419005" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1706747" xlink:to="loc_us-gaap_CommonClassBMember_1419005" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaap_AssetsAbstract_1418950" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419003" xlink:to="loc_us-gaap_AssetsAbstract_1418950" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="loc_us-gaap_AssetsCurrentAbstract_1418951" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1418950" xlink:to="loc_us-gaap_AssetsCurrentAbstract_1418951" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_1418952" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_1418951" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_1418952" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PrepaidExpenseCurrent" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_1418959" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_1418951" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_1418959" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherReceivablesNetCurrent" xlink:label="loc_us-gaap_OtherReceivablesNetCurrent_1418960" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_1418951" xlink:to="loc_us-gaap_OtherReceivablesNetCurrent_1418960" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_CovenantFeesReceivableNetCurrent" xlink:label="loc_fuse_CovenantFeesReceivableNetCurrent_1707056" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_1418951" xlink:to="loc_fuse_CovenantFeesReceivableNetCurrent_1707056" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MarketableSecuritiesCurrent" xlink:label="loc_us-gaap_MarketableSecuritiesCurrent_1418964" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_1418951" xlink:to="loc_us-gaap_MarketableSecuritiesCurrent_1418964" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_1706110" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_1418951" xlink:to="loc_us-gaap_AssetsCurrent_1706110" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_1418983" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1418950" xlink:to="loc_us-gaap_Assets_1418983" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1418986" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419003" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1418986" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_1418989" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1418986" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_1418989" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_1695543" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1418989" xlink:to="loc_us-gaap_AccountsPayableCurrent_1695543" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_1418990" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1418989" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_1418990" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NotesPayableCurrent" xlink:label="loc_us-gaap_NotesPayableCurrent_1706885" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1418989" xlink:to="loc_us-gaap_NotesPayableCurrent_1706885" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestPayableCurrent" xlink:label="loc_us-gaap_InterestPayableCurrent_1706886" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1418989" xlink:to="loc_us-gaap_InterestPayableCurrent_1706886" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredCompensationLiabilityCurrent" xlink:label="loc_us-gaap_DeferredCompensationLiabilityCurrent_1418996" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1418989" xlink:to="loc_us-gaap_DeferredCompensationLiabilityCurrent_1418996" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_1706121" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1418986" xlink:to="loc_us-gaap_LiabilitiesCurrent_1706121" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaap_Liabilities_1418997" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1418986" xlink:to="loc_us-gaap_Liabilities_1418997" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="loc_us-gaap_CommitmentsAndContingencies_1419006" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419003" xlink:to="loc_us-gaap_CommitmentsAndContingencies_1419006" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_1419007" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419003" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_1419007" use="optional" order="26" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="loc_us-gaap_StockholdersEquityAbstract_1419008" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419003" xlink:to="loc_us-gaap_StockholdersEquityAbstract_1419008" use="optional" order="27" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockValue" xlink:label="loc_us-gaap_PreferredStockValue_1419009" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1419008" xlink:to="loc_us-gaap_PreferredStockValue_1419009" use="optional" order="28" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockValue" xlink:label="loc_us-gaap_CommonStockValue_1419010" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1419008" xlink:to="loc_us-gaap_CommonStockValue_1419010" use="optional" order="29" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="loc_us-gaap_AdditionalPaidInCapital_1419011" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1419008" xlink:to="loc_us-gaap_AdditionalPaidInCapital_1419011" use="optional" order="30" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1419012" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1419008" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1419012" use="optional" order="31" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_1419013" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1419008" xlink:to="loc_us-gaap_StockholdersEquity_1419013" use="optional" order="32" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_1419014" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419003" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_1419014" use="optional" order="33" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/ConsolidatedBalanceSheetsParenthetical">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1419067" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1419064" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_StatementTable_1419064" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419065" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419064" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419065" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419066" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419065" xlink:to="loc_us-gaap_ClassOfStockDomain_1419066" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419066_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419065" xlink:to="loc_us-gaap_ClassOfStockDomain_1419066_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1419073" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419066" xlink:to="loc_us-gaap_CommonClassAMember_1419073" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaap_CommonClassBMember_1419075" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419066" xlink:to="loc_us-gaap_CommonClassBMember_1419075" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TemporaryEquityAxis" xlink:label="loc_fuse_TemporaryEquityAxis_1706844" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419064" xlink:to="loc_fuse_TemporaryEquityAxis_1706844" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TemporaryEquityDomain" xlink:label="loc_fuse_TemporaryEquityDomain_1706845" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_TemporaryEquityAxis_1706844" xlink:to="loc_fuse_TemporaryEquityDomain_1706845" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TemporaryEquityDomain" xlink:label="loc_fuse_TemporaryEquityDomain_1706845_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_TemporaryEquityAxis_1706844" xlink:to="loc_fuse_TemporaryEquityDomain_1706845_default" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityParOrStatedValuePerShare" xlink:label="loc_us-gaap_TemporaryEquityParOrStatedValuePerShare_1419077" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_TemporaryEquityParOrStatedValuePerShare_1419077" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesAuthorized" xlink:label="loc_us-gaap_TemporaryEquitySharesAuthorized_1419079" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_TemporaryEquitySharesAuthorized_1419079" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesIssued" xlink:label="loc_us-gaap_TemporaryEquitySharesIssued_1419081" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_TemporaryEquitySharesIssued_1419081" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesOutstanding" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_1419082" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_1419082" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_1419083" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_1419083" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_1419084" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_1419084" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="loc_us-gaap_PreferredStockSharesIssued_1419086" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_PreferredStockSharesIssued_1419086" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_1419087" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_1419087" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_1419088" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_1419088" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_1419089" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_1419089" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued" xlink:label="loc_us-gaap_CommonStockSharesIssued_1419090" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_CommonStockSharesIssued_1419090" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_1419091" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_1419091" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AllowanceForCreditLossOnCovenantFeesReceivableCurrent" xlink:label="loc_fuse_AllowanceForCreditLossOnCovenantFeesReceivableCurrent_1707057" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419067" xlink:to="loc_fuse_AllowanceForCreditLossOnCovenantFeesReceivableCurrent_1707057" use="optional" order="22" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/ConsolidatedStatementsOfOperations">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1419168" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1419165" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_StatementTable_1419165" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1695656" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419165" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1695656" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1695657" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1695656" xlink:to="loc_us-gaap_ClassOfStockDomain_1695657" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1695657_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1695656" xlink:to="loc_us-gaap_ClassOfStockDomain_1695657_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_RedeemableClassAMember" xlink:label="loc_fuse_RedeemableClassAMember_1706891" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1695657" xlink:to="loc_fuse_RedeemableClassAMember_1706891" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ClassANonRedeemableMember" xlink:label="loc_fuse_ClassANonRedeemableMember_1706893" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1695657" xlink:to="loc_fuse_ClassANonRedeemableMember_1706893" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ClassBNonRedeemableMember" xlink:label="loc_fuse_ClassBNonRedeemableMember_1706894" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1695657" xlink:to="loc_fuse_ClassBNonRedeemableMember_1706894" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PolicyholderBenefitsAndClaimsIncurredNet" xlink:label="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_1419144" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_1419144" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfessionalFees" xlink:label="loc_us-gaap_ProfessionalFees_1419148" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_ProfessionalFees_1419148" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DuesAndSubscriptions" xlink:label="loc_fuse_DuesAndSubscriptions_1419147" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_fuse_DuesAndSubscriptions_1419147" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_1707050" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_1707050" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_1706887" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_InterestExpenseDebt_1706887" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_FormationGeneralAndAdministrativeExpenses" xlink:label="loc_fuse_FormationGeneralAndAdministrativeExpenses_1706888" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_fuse_FormationGeneralAndAdministrativeExpenses_1706888" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingExpenses" xlink:label="loc_us-gaap_OperatingExpenses_1419151" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_OperatingExpenses_1419151" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_1419153" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_OperatingIncomeLoss_1419153" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_1419154" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_1419154" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MarketableSecuritiesRealizedGainLossExcludingOtherThanTemporaryImpairments" xlink:label="loc_us-gaap_MarketableSecuritiesRealizedGainLossExcludingOtherThanTemporaryImpairments_1706889" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_1419154" xlink:to="loc_us-gaap_MarketableSecuritiesRealizedGainLossExcludingOtherThanTemporaryImpairments_1706889" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentIncomeDividend" xlink:label="loc_us-gaap_InvestmentIncomeDividend_1706890" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_1419154" xlink:to="loc_us-gaap_InvestmentIncomeDividend_1706890" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_OtherNonOperatingIncomeMiscellaneousFee" xlink:label="loc_fuse_OtherNonOperatingIncomeMiscellaneousFee_1707131" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_1419154" xlink:to="loc_fuse_OtherNonOperatingIncomeMiscellaneousFee_1707131" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ProvisionForCreditLossesOnCovenantReceivable" xlink:label="loc_fuse_ProvisionForCreditLossesOnCovenantReceivable_1707132" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_1419154" xlink:to="loc_fuse_ProvisionForCreditLossesOnCovenantReceivable_1707132" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_1706839" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_1419154" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_1706839" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_1419157" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_NetIncomeLoss_1419157" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_1572140" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_1572140" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_1572141" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_1572141" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_1572145" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_EarningsPerShareBasic_1572145" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_1572147" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419168" xlink:to="loc_us-gaap_EarningsPerShareDiluted_1572147" use="optional" order="26" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/ConsolidatedStatementsOfChangesInClassAOrdinarySharesSubjectToPossibleRedemptionAndShareholdersDeficit">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1419193" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1419190" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_StatementTable_1419190" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419191" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419190" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419191" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419192" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419191" xlink:to="loc_us-gaap_ClassOfStockDomain_1419192" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419192_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419191" xlink:to="loc_us-gaap_ClassOfStockDomain_1419192_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1419194" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419192" xlink:to="loc_us-gaap_CommonClassAMember_1419194" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaap_CommonClassBMember_1419195" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419192" xlink:to="loc_us-gaap_CommonClassBMember_1419195" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_1419197" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419190" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_1419197" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_1419198" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1419197" xlink:to="loc_us-gaap_EquityComponentDomain_1419198" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_1419198_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1419197" xlink:to="loc_us-gaap_EquityComponentDomain_1419198_default" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_1419199" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1419198" xlink:to="loc_us-gaap_CommonStockMember_1419199" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_1419200" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1419198" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_1419200" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_1419202" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1419198" xlink:to="loc_us-gaap_RetainedEarningsMember_1419202" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis" xlink:label="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1706975" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419190" xlink:to="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1706975" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain" xlink:label="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1706976" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1706975" xlink:to="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1706976" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain" xlink:label="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1706976_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1706975" xlink:to="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1706976_default" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSubjectToMandatoryRedemptionMember" xlink:label="loc_us-gaap_CommonStockSubjectToMandatoryRedemptionMember_1706977" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1706976" xlink:to="loc_us-gaap_CommonStockSubjectToMandatoryRedemptionMember_1706977" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesOutstanding" xlink:label="loc_us-gaap_SharesOutstanding_1419209" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_SharesOutstanding_1419209" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_1419214" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_StockholdersEquity_1419214" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_1706895" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_1706895" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodValue" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodValue_1706896" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodValue_1706896" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_1706897" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_1706897" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfUnits" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfUnits_1706898" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfUnits_1706898" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AdjustmentToAdditionalCapitalWaiverOfAdministrativeServiceFees" xlink:label="loc_fuse_AdjustmentToAdditionalCapitalWaiverOfAdministrativeServiceFees_1707047" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_fuse_AdjustmentToAdditionalCapitalWaiverOfAdministrativeServiceFees_1707047" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_RemeasurementOfClassAOrdinarySharesSubjectToRedemptionToRedemptionValue" xlink:label="loc_fuse_RemeasurementOfClassAOrdinarySharesSubjectToRedemptionToRedemptionValue_1419226" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_fuse_RemeasurementOfClassAOrdinarySharesSubjectToRedemptionToRedemptionValue_1419226" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_1419227" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419193" xlink:to="loc_us-gaap_NetIncomeLoss_1419227" use="optional" order="25" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/OrganizationAndBusinessBackgroundAdditionalInformationDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1418975" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1418972" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_StatementTable_1418972" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1418973" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1418973" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1418974" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1418973" xlink:to="loc_us-gaap_ClassOfStockDomain_1418974" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1418974_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1418973" xlink:to="loc_us-gaap_ClassOfStockDomain_1418974_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1418981" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1418974" xlink:to="loc_us-gaap_CommonClassAMember_1418981" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaap_CommonClassBMember_1419094" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1418974" xlink:to="loc_us-gaap_CommonClassBMember_1419094" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_1418976" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_1418976" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1418977" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1418976" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1418977" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1418977_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1418976" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1418977_default" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IPOMember" xlink:label="loc_us-gaap_IPOMember_1418978" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1418977" xlink:to="loc_us-gaap_IPOMember_1418978" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="loc_us-gaap_OverAllotmentOptionMember_1418979" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1418977" xlink:to="loc_us-gaap_OverAllotmentOptionMember_1418979" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_1419036" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_1419036" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419037" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419036" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419037" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419037_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419036" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419037_default" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PrivatePlacementWarrantsMember" xlink:label="loc_fuse_PrivatePlacementWarrantsMember_1419041" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_1419037" xlink:to="loc_fuse_PrivatePlacementWarrantsMember_1419041" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419033" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419033" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419034" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419033" xlink:to="loc_us-gaap_RelatedPartyDomain_1419034" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419034_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419033" xlink:to="loc_us-gaap_RelatedPartyDomain_1419034_default" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_SponsorMember" xlink:label="loc_fuse_SponsorMember_1419035" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1419034" xlink:to="loc_fuse_SponsorMember_1419035" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_1419055" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_srt_RangeAxis_1419055" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1419056" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1419055" xlink:to="loc_srt_RangeMember_1419056" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1419056_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1419055" xlink:to="loc_srt_RangeMember_1419056_default" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_1419057" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_1419056" xlink:to="loc_srt_MaximumMember_1419057" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_1419058" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_1419056" xlink:to="loc_srt_MinimumMember_1419058" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis" xlink:label="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419062" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419062" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain" xlink:label="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419069" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419062" xlink:to="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419069" use="optional" order="26" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain" xlink:label="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419069_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419062" xlink:to="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419069_default" use="optional" order="27" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_1706934" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_us-gaap_DebtInstrumentAxis_1706934" use="optional" order="28" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1706935" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1706934" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1706935" use="optional" order="29" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1706935_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1706934" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1706935_default" use="optional" order="30" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommercialPaperMember" xlink:label="loc_us-gaap_CommercialPaperMember_1706936" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706935" xlink:to="loc_us-gaap_CommercialPaperMember_1706936" use="optional" order="31" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ThirdAmendedAndRestatedWorkingCapitalPromissoryNoteMember" xlink:label="loc_fuse_ThirdAmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707067" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706935" xlink:to="loc_fuse_ThirdAmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707067" use="optional" order="32" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ConvertiblePromissoryNoteMember" xlink:label="loc_fuse_ConvertiblePromissoryNoteMember_1707118" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706935" xlink:to="loc_fuse_ConvertiblePromissoryNoteMember_1707118" use="optional" order="33" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ConvertiblePromissoryNoteOneMember" xlink:label="loc_fuse_ConvertiblePromissoryNoteOneMember_1707119" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706935" xlink:to="loc_fuse_ConvertiblePromissoryNoteOneMember_1707119" use="optional" order="34" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ConvertiblePromissoryNoteTwoMember" xlink:label="loc_fuse_ConvertiblePromissoryNoteTwoMember_1707120" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706935" xlink:to="loc_fuse_ConvertiblePromissoryNoteTwoMember_1707120" use="optional" order="35" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_EventAxis" xlink:label="loc_fuse_EventAxis_1706981" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_fuse_EventAxis_1706981" use="optional" order="36" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_EventDomain" xlink:label="loc_fuse_EventDomain_1706982" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_EventAxis_1706981" xlink:to="loc_fuse_EventDomain_1706982" use="optional" order="37" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_EventDomain" xlink:label="loc_fuse_EventDomain_1706982_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_EventAxis_1706981" xlink:to="loc_fuse_EventDomain_1706982_default" use="optional" order="38" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InvestorAxis" xlink:label="loc_fuse_InvestorAxis_1706993" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_fuse_InvestorAxis_1706993" use="optional" order="39" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InvestorDomain" xlink:label="loc_fuse_InvestorDomain_1706994" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_InvestorAxis_1706993" xlink:to="loc_fuse_InvestorDomain_1706994" use="optional" order="40" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InvestorDomain" xlink:label="loc_fuse_InvestorDomain_1706994_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_InvestorAxis_1706993" xlink:to="loc_fuse_InvestorDomain_1706994_default" use="optional" order="41" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TrancheAxis" xlink:label="loc_fuse_TrancheAxis_1706998" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_fuse_TrancheAxis_1706998" use="optional" order="42" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TrancheDomain" xlink:label="loc_fuse_TrancheDomain_1706999" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_TrancheAxis_1706998" xlink:to="loc_fuse_TrancheDomain_1706999" use="optional" order="43" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TrancheDomain" xlink:label="loc_fuse_TrancheDomain_1706999_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_TrancheAxis_1706998" xlink:to="loc_fuse_TrancheDomain_1706999_default" use="optional" order="44" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementAxis" xlink:label="loc_fuse_AgreementAxis_1707008" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_fuse_AgreementAxis_1707008" use="optional" order="45" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementDomain" xlink:label="loc_fuse_AgreementDomain_1707009" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_AgreementAxis_1707008" xlink:to="loc_fuse_AgreementDomain_1707009" use="optional" order="46" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementDomain" xlink:label="loc_fuse_AgreementDomain_1707009_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_AgreementAxis_1707008" xlink:to="loc_fuse_AgreementDomain_1707009_default" use="optional" order="47" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_MergerAgreementAmendmentMember" xlink:label="loc_fuse_MergerAgreementAmendmentMember_1707061" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1707009" xlink:to="loc_fuse_MergerAgreementAmendmentMember_1707061" use="optional" order="48" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_SecondAmendedMergerAgreementMember" xlink:label="loc_fuse_SecondAmendedMergerAgreementMember_1707070" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1707009" xlink:to="loc_fuse_SecondAmendedMergerAgreementMember_1707070" use="optional" order="49" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1707064" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1418972" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1707064" use="optional" order="50" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1707065" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1707064" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1707065" use="optional" order="51" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1707065_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1707064" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1707065_default" use="optional" order="52" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_1707066" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_1707065" xlink:to="loc_us-gaap_SubsequentEventMember_1707066" use="optional" order="53" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1418982" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1418982" use="optional" order="54" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockConversionBasis" xlink:label="loc_us-gaap_CommonStockConversionBasis_1418984" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_CommonStockConversionBasis_1418984" use="optional" order="55" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_1418985" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_1418985" use="optional" order="56" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_1418987" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_1418987" use="optional" order="57" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1418988" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1418988" use="optional" order="58" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="loc_us-gaap_SharesIssuedPricePerShare_1418991" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_SharesIssuedPricePerShare_1418991" use="optional" order="59" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromIssuanceInitialPublicOffering" xlink:label="loc_us-gaap_ProceedsFromIssuanceInitialPublicOffering_1418992" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_ProceedsFromIssuanceInitialPublicOffering_1418992" use="optional" order="60" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ClassOfWarrantOrRightIssuedDuringPeriodWarrants" xlink:label="loc_fuse_ClassOfWarrantOrRightIssuedDuringPeriodWarrants_1419019" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_ClassOfWarrantOrRightIssuedDuringPeriodWarrants_1419019" use="optional" order="61" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockPricePerShare" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_1419021" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_1419021" use="optional" order="62" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromIssuanceOfWarrants" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfWarrants_1419023" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfWarrants_1419023" use="optional" order="63" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ClassOfWarrantsOrRightsRedemptionPricePerUnit" xlink:label="loc_fuse_ClassOfWarrantsOrRightsRedemptionPricePerUnit_1419046" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_ClassOfWarrantsOrRightsRedemptionPricePerUnit_1419046" use="optional" order="64" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_MinimumNoticePeriodToBeGivenToTheHoldersOfWarrants" xlink:label="loc_fuse_MinimumNoticePeriodToBeGivenToTheHoldersOfWarrants_1419047" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_MinimumNoticePeriodToBeGivenToTheHoldersOfWarrants_1419047" use="optional" order="65" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_CompanysOperatingAccount" xlink:label="loc_fuse_CompanysOperatingAccount_1419051" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_CompanysOperatingAccount_1419051" use="optional" order="66" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PercentageOfPublicSharesToBeRedeemedInCaseBusinessCombinationIsNotConsummated" xlink:label="loc_fuse_PercentageOfPublicSharesToBeRedeemedInCaseBusinessCombinationIsNotConsummated_1419053" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_PercentageOfPublicSharesToBeRedeemedInCaseBusinessCombinationIsNotConsummated_1419053" use="optional" order="67" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_1419085" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_1419085" use="optional" order="68" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueIssuedForServices" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueIssuedForServices_1419092" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueIssuedForServices_1419092" use="optional" order="69" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsHeldInTrust" xlink:label="loc_us-gaap_AssetsHeldInTrust_1706907" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_AssetsHeldInTrust_1706907" use="optional" order="70" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesOutstanding" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_1706908" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_1706908" use="optional" order="71" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement" xlink:label="loc_us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement_1706909" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement_1706909" use="optional" order="72" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityRedemptionPricePerShare" xlink:label="loc_us-gaap_TemporaryEquityRedemptionPricePerShare_1706910" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_TemporaryEquityRedemptionPricePerShare_1706910" use="optional" order="73" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsToAcquireRestrictedInvestments" xlink:label="loc_us-gaap_PaymentsToAcquireRestrictedInvestments_1706911" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_PaymentsToAcquireRestrictedInvestments_1706911" use="optional" order="74" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1706933" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1706933" use="optional" order="75" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AmountToBeDepositedInTheTrustAccountForEachExtension" xlink:label="loc_fuse_AmountToBeDepositedInTheTrustAccountForEachExtension_1706980" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_AmountToBeDepositedInTheTrustAccountForEachExtension_1706980" use="optional" order="76" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1707060" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1707060" use="optional" order="77" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_1707063" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_1707063" use="optional" order="78" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding" xlink:label="loc_fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding_1707068" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding_1707068" use="optional" order="79" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1707069" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1707069" use="optional" order="80" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_NetWorkingCapitalDeficit" xlink:label="loc_fuse_NetWorkingCapitalDeficit_1707071" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_fuse_NetWorkingCapitalDeficit_1707071" use="optional" order="81" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1707072" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1707072" use="optional" order="82" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NotesIssued1" xlink:label="loc_us-gaap_NotesIssued1_1707116" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_NotesIssued1_1707116" use="optional" order="83" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_1707117" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1418975" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_1707117" use="optional" order="84" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1419179" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1419176" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_us-gaap_StatementTable_1419176" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419177" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419176" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419177" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419178" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419177" xlink:to="loc_us-gaap_ClassOfStockDomain_1419178" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419178_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419177" xlink:to="loc_us-gaap_ClassOfStockDomain_1419178_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1419228" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419178" xlink:to="loc_us-gaap_CommonClassAMember_1419228" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis" xlink:label="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419206" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419176" xlink:to="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419206" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain" xlink:label="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419207" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419206" xlink:to="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419207" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain" xlink:label="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419207_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableAxis_1419206" xlink:to="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419207_default" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_FromTheCompletionOfBusinessCombinationMember" xlink:label="loc_fuse_FromTheCompletionOfBusinessCombinationMember_1419208" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisableDomain_1419207" xlink:to="loc_fuse_FromTheCompletionOfBusinessCombinationMember_1419208" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_1419210" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419176" xlink:to="loc_srt_RangeAxis_1419210" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1419211" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1419210" xlink:to="loc_srt_RangeMember_1419211" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1419211_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1419210" xlink:to="loc_srt_RangeMember_1419211_default" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_1706854" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419176" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_1706854" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1706855" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1706854" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1706855" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1706855_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1706854" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1706855_default" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_1706859" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419176" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_1706859" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1706860" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1706859" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1706860" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1706860_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1706859" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1706860_default" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_StatementsClassOfStockAxis" xlink:label="loc_fuse_StatementsClassOfStockAxis_1706938" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419176" xlink:to="loc_fuse_StatementsClassOfStockAxis_1706938" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_StatementsClassOfStockDomain" xlink:label="loc_fuse_StatementsClassOfStockDomain_1706939" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_StatementsClassOfStockAxis_1706938" xlink:to="loc_fuse_StatementsClassOfStockDomain_1706939" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_StatementsClassOfStockDomain" xlink:label="loc_fuse_StatementsClassOfStockDomain_1706939_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_StatementsClassOfStockAxis_1706938" xlink:to="loc_fuse_StatementsClassOfStockDomain_1706939_default" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsToAcquireRestrictedInvestments" xlink:label="loc_us-gaap_PaymentsToAcquireRestrictedInvestments_1419183" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_us-gaap_PaymentsToAcquireRestrictedInvestments_1419183" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TermOfRestrictedInvestments" xlink:label="loc_fuse_TermOfRestrictedInvestments_1419185" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_TermOfRestrictedInvestments_1419185" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PercentageOfPublicSharesToBeRedeemedInCaseBusinessCombinationIsNotConsummated" xlink:label="loc_fuse_PercentageOfPublicSharesToBeRedeemedInCaseBusinessCombinationIsNotConsummated_1419196" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_PercentageOfPublicSharesToBeRedeemedInCaseBusinessCombinationIsNotConsummated_1419196" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PeriodAfterWhichTheWarrantsAreExercisable" xlink:label="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisable_1419204" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_PeriodAfterWhichTheWarrantsAreExercisable_1419204" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesOutstanding" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_1419237" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_1419237" use="optional" order="26" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement" xlink:label="loc_us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement_1419244" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement_1419244" use="optional" order="27" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_1419250" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_1419250" use="optional" order="28" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnrecognizedTaxBenefits" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_1419255" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_1419255" use="optional" order="29" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_1419256" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_1419256" use="optional" order="30" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DelayedFeePayableOneMonthFromNow" xlink:label="loc_fuse_DelayedFeePayableOneMonthFromNow_1707074" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_DelayedFeePayableOneMonthFromNow_1707074" use="optional" order="31" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DelayedFeePayableTwoMonthsFromNow" xlink:label="loc_fuse_DelayedFeePayableTwoMonthsFromNow_1707075" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_DelayedFeePayableTwoMonthsFromNow_1707075" use="optional" order="32" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DelayedFeePayableThirdMonthAndThereafterPerMonth" xlink:label="loc_fuse_DelayedFeePayableThirdMonthAndThereafterPerMonth_1707076" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_DelayedFeePayableThirdMonthAndThereafterPerMonth_1707076" use="optional" order="33" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_OtherNonOperatingIncomeMiscellaneousFee" xlink:label="loc_fuse_OtherNonOperatingIncomeMiscellaneousFee_1707078" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_OtherNonOperatingIncomeMiscellaneousFee_1707078" use="optional" order="34" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_RemeasurementOfCommonStockSubjectToPossibleRedemption" xlink:label="loc_fuse_RemeasurementOfCommonStockSubjectToPossibleRedemption_1707073" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_RemeasurementOfCommonStockSubjectToPossibleRedemption_1707073" use="optional" order="35" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ProvisionForCreditLossesOnCovenantReceivable" xlink:label="loc_fuse_ProvisionForCreditLossesOnCovenantReceivable_1707079" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419179" xlink:to="loc_fuse_ProvisionForCreditLossesOnCovenantReceivable_1707079" use="optional" order="36" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfEarningsPerShareBasicAndDilutedDetail">
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems" xlink:label="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:label="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedTable_1419334" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedTable_1419334" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_StatementsClassOfStockAxis" xlink:label="loc_fuse_StatementsClassOfStockAxis_1419373" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedTable_1419334" xlink:to="loc_fuse_StatementsClassOfStockAxis_1419373" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_StatementsClassOfStockDomain" xlink:label="loc_fuse_StatementsClassOfStockDomain_1419376" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_StatementsClassOfStockAxis_1419373" xlink:to="loc_fuse_StatementsClassOfStockDomain_1419376" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_StatementsClassOfStockDomain" xlink:label="loc_fuse_StatementsClassOfStockDomain_1419376_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_StatementsClassOfStockAxis_1419373" xlink:to="loc_fuse_StatementsClassOfStockDomain_1419376_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_RedeemableClassAMember" xlink:label="loc_fuse_RedeemableClassAMember_1706945" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_StatementsClassOfStockDomain_1419376" xlink:to="loc_fuse_RedeemableClassAMember_1706945" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ClassANonRedeemableMember" xlink:label="loc_fuse_ClassANonRedeemableMember_1706950" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_StatementsClassOfStockDomain_1419376" xlink:to="loc_fuse_ClassANonRedeemableMember_1706950" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ClassBNonRedeemableMember" xlink:label="loc_fuse_ClassBNonRedeemableMember_1706951" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_StatementsClassOfStockDomain_1419376" xlink:to="loc_fuse_ClassBNonRedeemableMember_1706951" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis" xlink:label="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1419381" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedTable_1419334" xlink:to="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1419381" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain" xlink:label="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1419382" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1419381" xlink:to="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1419382" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain" xlink:label="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1419382_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis_1419381" xlink:to="loc_us-gaap_SharesSubjectToMandatoryRedemptionFinancialInstrumentDomain_1419382_default" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1706943" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedTable_1419334" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1706943" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1706944" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1706943" xlink:to="loc_us-gaap_ClassOfStockDomain_1706944" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1706944_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1706943" xlink:to="loc_us-gaap_ClassOfStockDomain_1706944_default" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesOutstanding" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_1706948" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_1706948" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_1419339" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_NetIncomeLoss_1419339" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment" xlink:label="loc_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_1706942" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_1706942" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_NetIncomeLossIncludingRemeasurementOfTemporaryEquityToRedemptionValue" xlink:label="loc_fuse_NetIncomeLossIncludingRemeasurementOfTemporaryEquityToRedemptionValue_1419342" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_fuse_NetIncomeLossIncludingRemeasurementOfTemporaryEquityToRedemptionValue_1419342" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityAccretionToRedemptionValue" xlink:label="loc_us-gaap_TemporaryEquityAccretionToRedemptionValue_1427044" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_TemporaryEquityAccretionToRedemptionValue_1427044" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AllocationOfNetIncomeLoss" xlink:label="loc_fuse_AllocationOfNetIncomeLoss_1706947" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_fuse_AllocationOfNetIncomeLoss_1706947" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_1572149" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_1572149" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_1572150" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_1572150" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_1572151" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_EarningsPerShareBasic_1572151" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_1572152" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_ScheduleOfEarningsPerShareBasicAndDilutedLineItems_1419337" xlink:to="loc_us-gaap_EarningsPerShareDiluted_1572152" use="optional" order="23" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/InitialPublicOfferingAdditionalInformationDetail">
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InitialPublicOfferingLineItems" xlink:label="loc_fuse_InitialPublicOfferingLineItems_1419459" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InitialPublicOfferingTable" xlink:label="loc_fuse_InitialPublicOfferingTable_1419289" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_fuse_InitialPublicOfferingLineItems_1419459" xlink:to="loc_fuse_InitialPublicOfferingTable_1419289" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_1419292" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fuse_InitialPublicOfferingTable_1419289" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_1419292" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419294" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1419292" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419294" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419294_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1419292" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419294_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IPOMember" xlink:label="loc_us-gaap_IPOMember_1419296" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419294" xlink:to="loc_us-gaap_IPOMember_1419296" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_1419299" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fuse_InitialPublicOfferingTable_1419289" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_1419299" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419300" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419299" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419300" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419300_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419299" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419300_default" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PublicWarrantMember" xlink:label="loc_fuse_PublicWarrantMember_1419305" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_1419300" xlink:to="loc_fuse_PublicWarrantMember_1419305" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419317" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fuse_InitialPublicOfferingTable_1419289" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419317" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419320" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419317" xlink:to="loc_us-gaap_ClassOfStockDomain_1419320" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419320_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419317" xlink:to="loc_us-gaap_ClassOfStockDomain_1419320_default" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1419321" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419320" xlink:to="loc_us-gaap_CommonClassAMember_1419321" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_1419324" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fuse_InitialPublicOfferingTable_1419289" xlink:to="loc_us-gaap_InvestmentTypeAxis_1419324" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_1419325" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_1419324" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_1419325" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_1419325_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_1419324" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_1419325_default" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_U.s.GovernmentSecuritiesMember" xlink:label="loc_fuse_U.s.GovernmentSecuritiesMember_1419326" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_1419325" xlink:to="loc_fuse_U.s.GovernmentSecuritiesMember_1419326" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1419460" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_InitialPublicOfferingLineItems_1419459" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1419460" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="loc_us-gaap_SharesIssuedPricePerShare_1419461" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_InitialPublicOfferingLineItems_1419459" xlink:to="loc_us-gaap_SharesIssuedPricePerShare_1419461" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1419462" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_InitialPublicOfferingLineItems_1419459" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1419462" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_1419465" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_InitialPublicOfferingLineItems_1419459" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_1419465" use="optional" order="21" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/PrivatePlacementAddtionalInformationDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:label="loc_us-gaap_ClassOfWarrantOrRightLineItems_1419251" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:label="loc_us-gaap_ClassOfWarrantOrRightTable_1419245" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_1419251" xlink:to="loc_us-gaap_ClassOfWarrantOrRightTable_1419245" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_1419246" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_1419245" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_1419246" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419247" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419246" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419247" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419247_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419246" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419247_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PrivatePlacementWarrantsMember" xlink:label="loc_fuse_PrivatePlacementWarrantsMember_1419249" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_1419247" xlink:to="loc_fuse_PrivatePlacementWarrantsMember_1419249" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419252" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_1419245" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419252" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419253" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419252" xlink:to="loc_us-gaap_RelatedPartyDomain_1419253" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419253_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419252" xlink:to="loc_us-gaap_RelatedPartyDomain_1419253_default" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_SponsorMember" xlink:label="loc_fuse_SponsorMember_1419254" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1419253" xlink:to="loc_fuse_SponsorMember_1419254" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ClassOfWarrantOrRightIssuedDuringPeriodWarrants" xlink:label="loc_fuse_ClassOfWarrantOrRightIssuedDuringPeriodWarrants_1419257" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_1419251" xlink:to="loc_fuse_ClassOfWarrantOrRightIssuedDuringPeriodWarrants_1419257" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockPricePerShare" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_1419258" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_1419251" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_1419258" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromIssuanceOfWarrants" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfWarrants_1419259" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_1419251" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfWarrants_1419259" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_1419265" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_1419251" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_1419265" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1419266" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_1419251" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1419266" use="optional" order="14" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/RelatedPartyTransactionsAdditionalInformationDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1419312" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1419309" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_StatementTable_1419309" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419310" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419309" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419310" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419311" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419310" xlink:to="loc_us-gaap_ClassOfStockDomain_1419311" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419311_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419310" xlink:to="loc_us-gaap_ClassOfStockDomain_1419311_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaap_CommonClassBMember_1419331" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419311" xlink:to="loc_us-gaap_CommonClassBMember_1419331" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_1419314" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419309" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_1419314" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_1419315" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_1419314" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_1419315" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_1419315_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_1419314" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_1419315_default" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_FounderSharesMember" xlink:label="loc_fuse_FounderSharesMember_1419318" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_1419315" xlink:to="loc_fuse_FounderSharesMember_1419318" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_UnsecuredPromissoryNoteMember" xlink:label="loc_fuse_UnsecuredPromissoryNoteMember_1419427" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_1419315" xlink:to="loc_fuse_UnsecuredPromissoryNoteMember_1419427" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_WorkingCapitalLoansMember" xlink:label="loc_fuse_WorkingCapitalLoansMember_1419428" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_1419315" xlink:to="loc_fuse_WorkingCapitalLoansMember_1419428" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419322" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419309" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419322" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419323" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419322" xlink:to="loc_us-gaap_RelatedPartyDomain_1419323" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419323_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419322" xlink:to="loc_us-gaap_RelatedPartyDomain_1419323_default" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_SponsorMember" xlink:label="loc_fuse_SponsorMember_1419327" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1419323" xlink:to="loc_fuse_SponsorMember_1419327" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualAxis" xlink:label="loc_srt_TitleOfIndividualAxis_1419379" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419309" xlink:to="loc_srt_TitleOfIndividualAxis_1419379" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1419380" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_1419379" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1419380" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1419380_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_1419379" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1419380_default" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_IndependentDirectorNomineeMember" xlink:label="loc_fuse_IndependentDirectorNomineeMember_1419384" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1419380" xlink:to="loc_fuse_IndependentDirectorNomineeMember_1419384" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_1706956" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419309" xlink:to="loc_us-gaap_DebtInstrumentAxis_1706956" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1706957" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1706956" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1706957" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1706957_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1706956" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1706957_default" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommercialPaperMember" xlink:label="loc_us-gaap_CommercialPaperMember_1706958" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706957" xlink:to="loc_us-gaap_CommercialPaperMember_1706958" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AmendedAndRestatedWorkingCapitalPromissoryNoteMember" xlink:label="loc_fuse_AmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707022" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706957" xlink:to="loc_fuse_AmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707022" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_SecondAmendedAndRestatedWorkingCapitalPromissoryNoteMember" xlink:label="loc_fuse_SecondAmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707124" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706957" xlink:to="loc_fuse_SecondAmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707124" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ThirdAmendedAndRestatedWorkingCapitalPromissoryNoteMember" xlink:label="loc_fuse_ThirdAmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707125" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706957" xlink:to="loc_fuse_ThirdAmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707125" use="optional" order="26" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_1706960" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419309" xlink:to="loc_srt_RangeAxis_1706960" use="optional" order="27" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1706961" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1706960" xlink:to="loc_srt_RangeMember_1706961" use="optional" order="28" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1706961_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1706960" xlink:to="loc_srt_RangeMember_1706961_default" use="optional" order="29" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1707023" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419309" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1707023" use="optional" order="30" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1707024" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1707023" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1707024" use="optional" order="31" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1707024_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1707023" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1707024_default" use="optional" order="32" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_1707025" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_1707024" xlink:to="loc_us-gaap_SubsequentEventMember_1707025" use="optional" order="33" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1419350" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1419350" use="optional" order="34" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_1419349" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_1419349" use="optional" order="35" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AggregateOfSharesSubjectToForfeiture" xlink:label="loc_fuse_AggregateOfSharesSubjectToForfeiture_1419352" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_AggregateOfSharesSubjectToForfeiture_1419352" use="optional" order="36" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PercentageOfIssuedAndOutstandingSharesAfterInitialPublicOfferingCollectivelyHeldByInitialStockholders" xlink:label="loc_fuse_PercentageOfIssuedAndOutstandingSharesAfterInitialPublicOfferingCollectivelyHeldByInitialStockholders_1419371" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_PercentageOfIssuedAndOutstandingSharesAfterInitialPublicOfferingCollectivelyHeldByInitialStockholders_1419371" use="optional" order="37" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TransferAssignOrSellAnySharesOrWarrantsAfterCompletionOfInitialBusinessCombinationThresholdTradingDays" xlink:label="loc_fuse_TransferAssignOrSellAnySharesOrWarrantsAfterCompletionOfInitialBusinessCombinationThresholdTradingDays_1419385" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_TransferAssignOrSellAnySharesOrWarrantsAfterCompletionOfInitialBusinessCombinationThresholdTradingDays_1419385" use="optional" order="38" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TransferAssignOrSellAnySharesOrWarrantsAfterCompletionOfInitialBusinessCombinationThresholdConsecutiveTradingDays" xlink:label="loc_fuse_TransferAssignOrSellAnySharesOrWarrantsAfterCompletionOfInitialBusinessCombinationThresholdConsecutiveTradingDays_1419390" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_TransferAssignOrSellAnySharesOrWarrantsAfterCompletionOfInitialBusinessCombinationThresholdConsecutiveTradingDays_1419390" use="optional" order="39" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ThresholdPeriodAfterBusinessCombinationInWhichSpecifiedTradingDaysWithinAnySpecifiedTradingDayPeriodCommences" xlink:label="loc_fuse_ThresholdPeriodAfterBusinessCombinationInWhichSpecifiedTradingDaysWithinAnySpecifiedTradingDayPeriodCommences_1419395" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_ThresholdPeriodAfterBusinessCombinationInWhichSpecifiedTradingDaysWithinAnySpecifiedTradingDayPeriodCommences_1419395" use="optional" order="40" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PayableForOfficeAndAdministrationSupportServicesPerMonth" xlink:label="loc_fuse_PayableForOfficeAndAdministrationSupportServicesPerMonth_1707033" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_PayableForOfficeAndAdministrationSupportServicesPerMonth_1707033" use="optional" order="41" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_1419419" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_1419419" use="optional" order="42" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentMaturityDateRangeEnd1" xlink:label="loc_us-gaap_DebtInstrumentMaturityDateRangeEnd1_1419421" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_DebtInstrumentMaturityDateRangeEnd1_1419421" use="optional" order="43" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RepaymentsOfRelatedPartyDebt" xlink:label="loc_us-gaap_RepaymentsOfRelatedPartyDebt_1419422" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_RepaymentsOfRelatedPartyDebt_1419422" use="optional" order="44" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherReceivables" xlink:label="loc_us-gaap_OtherReceivables_1419423" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_OtherReceivables_1419423" use="optional" order="45" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent" xlink:label="loc_us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent_1419431" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent_1419431" use="optional" order="46" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1419432" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1419432" use="optional" order="47" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1706955" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1706955" use="optional" order="48" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromRelatedPartyDebt" xlink:label="loc_us-gaap_ProceedsFromRelatedPartyDebt_1706964" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_ProceedsFromRelatedPartyDebt_1706964" use="optional" order="49" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestPayableCurrentAndNoncurrent" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent_1706965" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_us-gaap_InterestPayableCurrentAndNoncurrent_1706965" use="optional" order="50" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AdjustmentToAdditionalCapitalWaiverOfAdministrativeServiceFees" xlink:label="loc_fuse_AdjustmentToAdditionalCapitalWaiverOfAdministrativeServiceFees_1707045" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_AdjustmentToAdditionalCapitalWaiverOfAdministrativeServiceFees_1707045" use="optional" order="51" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding" xlink:label="loc_fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding_1707099" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419312" xlink:to="loc_fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding_1707099" use="optional" order="52" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/ShareholdersDeficitAdditionalInformationDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_1419543" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_1419542" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_1419542" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419654" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1419542" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419654" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419655" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419654" xlink:to="loc_us-gaap_RelatedPartyDomain_1419655" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419655_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419654" xlink:to="loc_us-gaap_RelatedPartyDomain_1419655_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_1419648" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1419542" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_1419648" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_1419649" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_1419648" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_1419649" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_1419649_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_1419648" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_1419649_default" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419625" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1419542" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419625" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419626" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419625" xlink:to="loc_us-gaap_ClassOfStockDomain_1419626" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419626_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419625" xlink:to="loc_us-gaap_ClassOfStockDomain_1419626_default" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1419628" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419626" xlink:to="loc_us-gaap_CommonClassAMember_1419628" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaap_CommonClassBMember_1419630" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419626" xlink:to="loc_us-gaap_CommonClassBMember_1419630" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_1419596" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1419542" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_1419596" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419597" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419596" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419597" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1419597_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1419596" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1419597_default" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PrivatePlacementWarrantsMember" xlink:label="loc_fuse_PrivatePlacementWarrantsMember_1419599" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_1419597" xlink:to="loc_fuse_PrivatePlacementWarrantsMember_1419599" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_PublicWarrantMember" xlink:label="loc_fuse_PublicWarrantMember_1419601" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_1419597" xlink:to="loc_fuse_PublicWarrantMember_1419601" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TriggerEventAxis" xlink:label="loc_fuse_TriggerEventAxis_1419604" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1419542" xlink:to="loc_fuse_TriggerEventAxis_1419604" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TriggerEventDomain" xlink:label="loc_fuse_TriggerEventDomain_1419606" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_TriggerEventAxis_1419604" xlink:to="loc_fuse_TriggerEventDomain_1419606" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TriggerEventDomain" xlink:label="loc_fuse_TriggerEventDomain_1419606_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_TriggerEventAxis_1419604" xlink:to="loc_fuse_TriggerEventDomain_1419606_default" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_EventTriggeringWarrantRedemptionMember" xlink:label="loc_fuse_EventTriggeringWarrantRedemptionMember_1419609" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_TriggerEventDomain_1419606" xlink:to="loc_fuse_EventTriggeringWarrantRedemptionMember_1419609" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_WarrantRedemptionTriggerPriceAxis" xlink:label="loc_fuse_WarrantRedemptionTriggerPriceAxis_1419610" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_1419542" xlink:to="loc_fuse_WarrantRedemptionTriggerPriceAxis_1419610" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_WarrantRedemptionTriggerPriceDomain" xlink:label="loc_fuse_WarrantRedemptionTriggerPriceDomain_1419612" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_WarrantRedemptionTriggerPriceAxis_1419610" xlink:to="loc_fuse_WarrantRedemptionTriggerPriceDomain_1419612" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_WarrantRedemptionTriggerPriceDomain" xlink:label="loc_fuse_WarrantRedemptionTriggerPriceDomain_1419612_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_WarrantRedemptionTriggerPriceAxis_1419610" xlink:to="loc_fuse_WarrantRedemptionTriggerPriceDomain_1419612_default" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TriggerPriceOneMember" xlink:label="loc_fuse_TriggerPriceOneMember_1419615" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_WarrantRedemptionTriggerPriceDomain_1419612" xlink:to="loc_fuse_TriggerPriceOneMember_1419615" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_TriggerPriceTwoMember" xlink:label="loc_fuse_TriggerPriceTwoMember_1419837" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_WarrantRedemptionTriggerPriceDomain_1419612" xlink:to="loc_fuse_TriggerPriceTwoMember_1419837" use="optional" order="26" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_1419546" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_1419546" use="optional" order="27" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_1419547" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_1419547" use="optional" order="28" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="loc_us-gaap_PreferredStockSharesIssued_1419548" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_PreferredStockSharesIssued_1419548" use="optional" order="29" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_1419549" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_1419549" use="optional" order="30" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_1419550" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_1419550" use="optional" order="31" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_1419551" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_1419551" use="optional" order="32" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockVotingRights" xlink:label="loc_us-gaap_CommonStockVotingRights_1419552" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_CommonStockVotingRights_1419552" use="optional" order="33" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued" xlink:label="loc_us-gaap_CommonStockSharesIssued_1419553" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_CommonStockSharesIssued_1419553" use="optional" order="34" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_1419554" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_1419554" use="optional" order="35" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesIssued" xlink:label="loc_us-gaap_TemporaryEquitySharesIssued_1419686" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_TemporaryEquitySharesIssued_1419686" use="optional" order="36" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquitySharesOutstanding" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_1419555" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_1419555" use="optional" order="37" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Warrantexerciseperiodconditionone" xlink:label="loc_fuse_Warrantexerciseperiodconditionone_1419569" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Warrantexerciseperiodconditionone_1419569" use="optional" order="38" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Warrantexerciseperiodconditiontwo" xlink:label="loc_fuse_Warrantexerciseperiodconditiontwo_1419571" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Warrantexerciseperiodconditiontwo_1419571" use="optional" order="39" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Maximumthresholdperiodforfilingregistrationstatementafterbusinesscombination" xlink:label="loc_fuse_Maximumthresholdperiodforfilingregistrationstatementafterbusinesscombination_1419572" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Maximumthresholdperiodforfilingregistrationstatementafterbusinesscombination_1419572" use="optional" order="40" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Maximumthresholdperiodforregistrationstatementtobecomeeffectiveafterbusinesscombination" xlink:label="loc_fuse_Maximumthresholdperiodforregistrationstatementtobecomeeffectiveafterbusinesscombination_1419574" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Maximumthresholdperiodforregistrationstatementtobecomeeffectiveafterbusinesscombination_1419574" use="optional" order="41" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Classofwarrantorrightredemptionpriceofwarrantsorrights" xlink:label="loc_fuse_Classofwarrantorrightredemptionpriceofwarrantsorrights_1419578" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Classofwarrantorrightredemptionpriceofwarrantsorrights_1419578" use="optional" order="42" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Redemptionperiod" xlink:label="loc_fuse_Redemptionperiod_1419579" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Redemptionperiod_1419579" use="optional" order="43" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Warrantredemptionconditionminimumshareprice" xlink:label="loc_fuse_Warrantredemptionconditionminimumshareprice_1419580" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Warrantredemptionconditionminimumshareprice_1419580" use="optional" order="44" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Classofwarrantorrightredemptionofwarrantsorrightsthresholdtradingdays" xlink:label="loc_fuse_Classofwarrantorrightredemptionofwarrantsorrightsthresholdtradingdays_1419581" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Classofwarrantorrightredemptionofwarrantsorrightsthresholdtradingdays_1419581" use="optional" order="45" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Classofwarrantorrightredemptionofwarrantsorrightsthresholdconsecutivetradingdays" xlink:label="loc_fuse_Classofwarrantorrightredemptionofwarrantsorrightsthresholdconsecutivetradingdays_1419582" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Classofwarrantorrightredemptionofwarrantsorrightsthresholdconsecutivetradingdays_1419582" use="optional" order="46" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharePrice" xlink:label="loc_us-gaap_SharePrice_1419583" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_SharePrice_1419583" use="optional" order="47" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Percentageofequityproceedsfrombusinesscombinationasapercentageoftotalproceeds" xlink:label="loc_fuse_Percentageofequityproceedsfrombusinesscombinationasapercentageoftotalproceeds_1419584" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Percentageofequityproceedsfrombusinesscombinationasapercentageoftotalproceeds_1419584" use="optional" order="48" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Numberoftradingdays" xlink:label="loc_fuse_Numberoftradingdays_1419587" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Numberoftradingdays_1419587" use="optional" order="49" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Redemptiontriggerpriceasapercentageofnewlyissuedprice" xlink:label="loc_fuse_Redemptiontriggerpriceasapercentageofnewlyissuedprice_1419588" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Redemptiontriggerpriceasapercentageofnewlyissuedprice_1419588" use="optional" order="50" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Classofwarrantsorrightsredemptiontriggerprice" xlink:label="loc_fuse_Classofwarrantsorrightsredemptiontriggerprice_1419589" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Classofwarrantsorrightsredemptiontriggerprice_1419589" use="optional" order="51" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_Warrantnontransferableperiod" xlink:label="loc_fuse_Warrantnontransferableperiod_1419594" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_fuse_Warrantnontransferableperiod_1419594" use="optional" order="52" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1419633" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_1419633" use="optional" order="53" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockConversionBasis" xlink:label="loc_us-gaap_CommonStockConversionBasis_1706842" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_CommonStockConversionBasis_1706842" use="optional" order="54" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement" xlink:label="loc_us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement_1706979" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_1419543" xlink:to="loc_us-gaap_TemporaryEquityAggregateAmountOfRedemptionRequirement_1706979" use="optional" order="55" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/CommitmentsAndContingenciesAdditionalInformationDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1419103" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1419100" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_StatementTable_1419100" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1419101" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419100" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1419101" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419102" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419101" xlink:to="loc_us-gaap_ClassOfStockDomain_1419102" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_1419102_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1419101" xlink:to="loc_us-gaap_ClassOfStockDomain_1419102_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaap_CommonClassAMember_1419104" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419102" xlink:to="loc_us-gaap_CommonClassAMember_1419104" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaap_CommonClassBMember_1707097" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_1419102" xlink:to="loc_us-gaap_CommonClassBMember_1707097" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419107" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419100" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419107" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419108" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419107" xlink:to="loc_us-gaap_RelatedPartyDomain_1419108" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1419108_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1419107" xlink:to="loc_us-gaap_RelatedPartyDomain_1419108_default" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_SponsorMember" xlink:label="loc_fuse_SponsorMember_1707027" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1419108" xlink:to="loc_fuse_SponsorMember_1707027" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_1419111" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419100" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_1419111" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419112" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1419111" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419112" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419112_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1419111" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419112_default" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="loc_us-gaap_OverAllotmentOptionMember_1419114" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1419112" xlink:to="loc_us-gaap_OverAllotmentOptionMember_1419114" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementAxis" xlink:label="loc_fuse_AgreementAxis_1419115" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419100" xlink:to="loc_fuse_AgreementAxis_1419115" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementDomain" xlink:label="loc_fuse_AgreementDomain_1419116" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_AgreementAxis_1419115" xlink:to="loc_fuse_AgreementDomain_1419116" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementDomain" xlink:label="loc_fuse_AgreementDomain_1419116_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_AgreementAxis_1419115" xlink:to="loc_fuse_AgreementDomain_1419116_default" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_UnderwritingAgreementMember" xlink:label="loc_fuse_UnderwritingAgreementMember_1419117" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1419116" xlink:to="loc_fuse_UnderwritingAgreementMember_1419117" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_FounderTransactionBonusAgreementMember" xlink:label="loc_fuse_FounderTransactionBonusAgreementMember_1707037" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1419116" xlink:to="loc_fuse_FounderTransactionBonusAgreementMember_1707037" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_CapitalMarketsAdvisoryAgreementMember" xlink:label="loc_fuse_CapitalMarketsAdvisoryAgreementMember_1707093" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1419116" xlink:to="loc_fuse_CapitalMarketsAdvisoryAgreementMember_1707093" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ConsultingAgreementsMember" xlink:label="loc_fuse_ConsultingAgreementsMember_1707136" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1419116" xlink:to="loc_fuse_ConsultingAgreementsMember_1707136" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AdvisoryAgreementMember" xlink:label="loc_fuse_AdvisoryAgreementMember_1707137" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1419116" xlink:to="loc_fuse_AdvisoryAgreementMember_1707137" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_FinancialServicesAgreementMember" xlink:label="loc_fuse_FinancialServicesAgreementMember_1707145" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1419116" xlink:to="loc_fuse_FinancialServicesAgreementMember_1707145" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InvestorAxis" xlink:label="loc_fuse_InvestorAxis_1707038" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419100" xlink:to="loc_fuse_InvestorAxis_1707038" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InvestorDomain" xlink:label="loc_fuse_InvestorDomain_1707039" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_InvestorAxis_1707038" xlink:to="loc_fuse_InvestorDomain_1707039" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InvestorDomain" xlink:label="loc_fuse_InvestorDomain_1707039_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_InvestorAxis_1707038" xlink:to="loc_fuse_InvestorDomain_1707039_default" use="optional" order="26" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualAxis" xlink:label="loc_srt_TitleOfIndividualAxis_1707041" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1419100" xlink:to="loc_srt_TitleOfIndividualAxis_1707041" use="optional" order="27" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1707042" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_1707041" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1707042" use="optional" order="28" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1707042_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_1707041" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1707042_default" use="optional" order="29" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_FounderAndChiefExecutiveOfficerMember" xlink:label="loc_fuse_FounderAndChiefExecutiveOfficerMember_1707043" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_1707042" xlink:to="loc_fuse_FounderAndChiefExecutiveOfficerMember_1707043" use="optional" order="30" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesSubscribedButUnissued" xlink:label="loc_us-gaap_CommonStockSharesSubscribedButUnissued_1419119" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_CommonStockSharesSubscribedButUnissued_1419119" use="optional" order="31" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsForUnderwritingExpense" xlink:label="loc_us-gaap_PaymentsForUnderwritingExpense_1419123" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_PaymentsForUnderwritingExpense_1419123" use="optional" order="32" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DeferredFeePerShares" xlink:label="loc_fuse_DeferredFeePerShares_1419127" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_DeferredFeePerShares_1419127" use="optional" order="33" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent" xlink:label="loc_us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent_1419128" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent_1419128" use="optional" order="34" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_UnderwritingDiscountPerShare" xlink:label="loc_fuse_UnderwritingDiscountPerShare_1419141" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_UnderwritingDiscountPerShare_1419141" use="optional" order="35" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_NumberOfDaysGrantedToUnderwritersToSubscribeSharesPursuantToOverallotmentOption" xlink:label="loc_fuse_NumberOfDaysGrantedToUnderwritersToSubscribeSharesPursuantToOverallotmentOption_1419184" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_NumberOfDaysGrantedToUnderwritersToSubscribeSharesPursuantToOverallotmentOption_1419184" use="optional" order="36" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_InterseTransferOfSharesToBeMade" xlink:label="loc_fuse_InterseTransferOfSharesToBeMade_1707026" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_InterseTransferOfSharesToBeMade_1707026" use="optional" order="37" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AdvisoryFeePaidInCash" xlink:label="loc_fuse_AdvisoryFeePaidInCash_1707091" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_AdvisoryFeePaidInCash_1707091" use="optional" order="38" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AdvisoryPaidInShareForPostBusinessCombination" xlink:label="loc_fuse_AdvisoryPaidInShareForPostBusinessCombination_1707092" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_AdvisoryPaidInShareForPostBusinessCombination_1707092" use="optional" order="39" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_1707094" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_1707094" use="optional" order="40" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SaleOfStockPricePerShare" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_1707095" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_1707095" use="optional" order="41" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredCompensationArrangementWithIndividualDescription" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualDescription_1707098" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualDescription_1707098" use="optional" order="42" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AggregateOfSaleOfStockNumberOfSharesIssuedInTransaction" xlink:label="loc_fuse_AggregateOfSaleOfStockNumberOfSharesIssuedInTransaction_1707134" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_AggregateOfSaleOfStockNumberOfSharesIssuedInTransaction_1707134" use="optional" order="43" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_UnrecognizedStockBasedCompensationExpense" xlink:label="loc_fuse_UnrecognizedStockBasedCompensationExpense_1707135" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_UnrecognizedStockBasedCompensationExpense_1707135" use="optional" order="44" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IntercompanyAgreementsDescription" xlink:label="loc_us-gaap_IntercompanyAgreementsDescription_1707144" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_IntercompanyAgreementsDescription_1707144" use="optional" order="45" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_NumberOfSharesIssuedAsManagementFeePaid" xlink:label="loc_fuse_NumberOfSharesIssuedAsManagementFeePaid_1707146" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_fuse_NumberOfSharesIssuedAsManagementFeePaid_1707146" use="optional" order="46" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_1707147" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1419103" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_1707147" use="optional" order="47" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/FairValueMeasurementsSummaryOfTheFairValueHierarchyTheCompanySAssetsAndLiabilitiesThatWereAccountedForAtFairValueOnARecurringBasisDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1706793" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1706792" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1706793" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1706792" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_1706796" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1706792" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_1706796" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_1706797" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_1706796" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_1706797" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_1706797_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_1706796" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_1706797_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_1706798" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_1706797" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_1706798" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_1706799" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1706792" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_1706799" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1706800" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_1706799" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1706800" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1706800_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_1706799" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1706800_default" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_1706863" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1706800" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_1706863" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1706802" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1706792" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1706802" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1706803" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1706802" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1706803" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1706803_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_1706802" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1706803_default" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_1706804" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1706803" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_1706804" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosureAbstract" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_1706794" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1706793" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_1706794" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_1706795" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_1706794" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_1706795" use="optional" order="15" />
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://cslm.com/role/SubsequentEventsAdditionalInformationDetail">
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_1706867" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_1706866" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_us-gaap_SubsequentEventTable_1706866" xbrldt:contextElement="segment" xbrldt:closed="true" use="optional" order="1" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1706868" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_1706866" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1706868" use="optional" order="2" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1706869" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1706868" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1706869" use="optional" order="3" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1706869_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1706868" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1706869_default" use="optional" order="4" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_1706870" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_1706869" xlink:to="loc_us-gaap_SubsequentEventMember_1706870" use="optional" order="5" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_1706871" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_1706866" xlink:to="loc_us-gaap_DebtInstrumentAxis_1706871" use="optional" order="6" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1706872" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1706871" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1706872" use="optional" order="7" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1706872_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1706871" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1706872_default" use="optional" order="8" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AmendedAndRestatedWorkingCapitalPromissoryNoteMember" xlink:label="loc_fuse_AmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707028" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706872" xlink:to="loc_fuse_AmendedAndRestatedWorkingCapitalPromissoryNoteMember_1707028" use="optional" order="9" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ConvertablePromissoryNoteMember" xlink:label="loc_fuse_ConvertablePromissoryNoteMember_1707086" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706872" xlink:to="loc_fuse_ConvertablePromissoryNoteMember_1707086" use="optional" order="10" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ConvertablePromissoryNoteOneMember" xlink:label="loc_fuse_ConvertablePromissoryNoteOneMember_1707087" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706872" xlink:to="loc_fuse_ConvertablePromissoryNoteOneMember_1707087" use="optional" order="11" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_ConvertablePromissoryNoteTwoMember" xlink:label="loc_fuse_ConvertablePromissoryNoteTwoMember_1707088" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1706872" xlink:to="loc_fuse_ConvertablePromissoryNoteTwoMember_1707088" use="optional" order="12" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_1706970" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_1706866" xlink:to="loc_srt_RangeAxis_1706970" use="optional" order="13" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1706971" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1706970" xlink:to="loc_srt_RangeMember_1706971" use="optional" order="14" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_1706971_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1706970" xlink:to="loc_srt_RangeMember_1706971_default" use="optional" order="15" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementAxis" xlink:label="loc_fuse_AgreementAxis_1707082" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_1706866" xlink:to="loc_fuse_AgreementAxis_1707082" use="optional" order="16" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementDomain" xlink:label="loc_fuse_AgreementDomain_1707083" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fuse_AgreementAxis_1707082" xlink:to="loc_fuse_AgreementDomain_1707083" use="optional" order="17" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_AgreementDomain" xlink:label="loc_fuse_AgreementDomain_1707083_default" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fuse_AgreementAxis_1707082" xlink:to="loc_fuse_AgreementDomain_1707083_default" use="optional" order="18" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_SecondAmendedMergerAgreementMember" xlink:label="loc_fuse_SecondAmendedMergerAgreementMember_1707084" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fuse_AgreementDomain_1707083" xlink:to="loc_fuse_SecondAmendedMergerAgreementMember_1707084" use="optional" order="19" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_1706874" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_1706874" use="optional" order="20" />
<loc xlink:type="locator" xlink:href="fuse-20241231.xsd#fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding" xlink:label="loc_fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding_1707080" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_fuse_DebtinstrumentPaymentPrincipalAndAccruedInterestOutstanding_1707080" use="optional" order="21" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1707081" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1707081" use="optional" order="22" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1707085" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1707085" use="optional" order="23" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NotesIssued1" xlink:label="loc_us-gaap_NotesIssued1_1707089" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_us-gaap_NotesIssued1_1707089" use="optional" order="24" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_1707090" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_1707090" use="optional" order="25" />
<loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsToAcquireRestrictedInvestments" xlink:label="loc_us-gaap_PaymentsToAcquireRestrictedInvestments_1707130" />
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_1706867" xlink:to="loc_us-gaap_PaymentsToAcquireRestrictedInvestments_1707130" use="optional" order="26" />
</definitionLink>
</linkbase>
