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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019fb4bc-6790-734b-af7f-d35f913d2685,g:8ede5b8a-4c6c-4f25-be9b-ed46b82fd5a4-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="simple" xlink:href="drs-20260930.xsd#ConsolidatedStatementsofCashFlowsUnaudited"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019fb4bc-6857-75d2-b5cd-322b9ad8e39f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:to="loc_us-gaap_StatementTable_019fb4bc-6857-75d2-b5cd-322b9ad8e39f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-6857-7d4e-b804-6f5953396f28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019fb4bc-6857-75d2-b5cd-322b9ad8e39f" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-6857-7d4e-b804-6f5953396f28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fb4bc-6857-7d4e-b804-6f5953396f28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-6857-7d4e-b804-6f5953396f28" xlink:to="loc_us-gaap_RelatedPartyDomain_019fb4bc-6857-7d4e-b804-6f5953396f28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fb4bc-6857-72a0-9022-0bfd73a61ef8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-6857-7d4e-b804-6f5953396f28" xlink:to="loc_us-gaap_RelatedPartyDomain_019fb4bc-6857-72a0-9022-0bfd73a61ef8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_019fb4bc-6857-7fcf-9dad-80bbd37a4416" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fb4bc-6857-72a0-9022-0bfd73a61ef8" xlink:to="loc_us-gaap_NonrelatedPartyMember_019fb4bc-6857-7fcf-9dad-80bbd37a4416" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019fb4bc-6857-7b57-a6b0-ea4b7b8bdcf2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fb4bc-6857-72a0-9022-0bfd73a61ef8" xlink:to="loc_us-gaap_RelatedPartyMember_019fb4bc-6857-7b57-a6b0-ea4b7b8bdcf2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-74ce-bbc2-c71593060e24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-74ce-bbc2-c71593060e24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019fb4bc-6857-7bdf-ba38-e94ebd41d623" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-74ce-bbc2-c71593060e24" xlink:to="loc_us-gaap_NetIncomeLoss_019fb4bc-6857-7bdf-ba38-e94ebd41d623" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-7959-a44d-9d413ef85b4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-74ce-bbc2-c71593060e24" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-7959-a44d-9d413ef85b4e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019fb4bc-6857-7ea7-9e85-a949922441b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-7959-a44d-9d413ef85b4e" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019fb4bc-6857-7ea7-9e85-a949922441b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019fb4bc-6857-74c3-b70c-5b7a6a82094a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-7959-a44d-9d413ef85b4e" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019fb4bc-6857-74c3-b70c-5b7a6a82094a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019fb4bc-6857-7d20-b3e3-b7a1cce50252" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-7959-a44d-9d413ef85b4e" xlink:to="loc_us-gaap_ShareBasedCompensation_019fb4bc-6857-7d20-b3e3-b7a1cce50252" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-7959-a44d-9d413ef85b4e" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019fb4bc-6857-7889-8e77-d10d7aea0ceb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019fb4bc-6857-7889-8e77-d10d7aea0ceb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_019fb4bc-6857-7328-9c38-ac778f2669b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_019fb4bc-6857-7328-9c38-ac778f2669b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_019fb4bc-6857-732b-8c79-3f51f99842eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_019fb4bc-6857-732b-8c79-3f51f99842eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidExpense_019fb4bc-6857-73eb-889f-5bcfa7e082cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInPrepaidExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidExpense_019fb4bc-6857-73eb-889f-5bcfa7e082cf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_019fb4bc-6857-72be-90f8-fed37e648f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_019fb4bc-6857-72be-90f8-fed37e648f0d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_019fb4bc-6857-7361-9307-3d0a821a4200" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_019fb4bc-6857-7361-9307-3d0a821a4200" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_019fb4bc-6857-77a2-8861-b968716ed295" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_019fb4bc-6857-77a2-8861-b968716ed295" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019fb4bc-6857-73b7-9805-608f33aff80f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019fb4bc-6857-73b7-9805-608f33aff80f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_019fb4bc-6857-7c16-895e-9b4f96758620" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_019fb4bc-6857-7c16-895e-9b4f96758620" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentLiabilities_019fb4bc-6857-76c7-9679-6d27c7276faf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentLiabilities_019fb4bc-6857-76c7-9679-6d27c7276faf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_019fb4bc-6857-7a6c-b415-b8e33e71e3eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019fb4bc-6857-7db4-87ee-145aac382d28" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_019fb4bc-6857-7a6c-b415-b8e33e71e3eb" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019fb4bc-6857-7bf5-8cb0-dd180f29eddf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019fb4bc-6857-74ce-bbc2-c71593060e24" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019fb4bc-6857-7bf5-8cb0-dd180f29eddf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019fb4bc-6857-7522-9bc5-5408f0870dad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019fb4bc-6857-7522-9bc5-5408f0870dad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019fb4bc-6857-776c-a697-f5b97bca30ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019fb4bc-6857-7522-9bc5-5408f0870dad" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019fb4bc-6857-776c-a697-f5b97bca30ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_01a13f7b-50fe-7ee3-9941-fa7020ae2a3b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfProductiveAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019fb4bc-6857-7522-9bc5-5408f0870dad" xlink:to="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_01a13f7b-50fe-7ee3-9941-fa7020ae2a3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromInvestments_01a0331c-a315-72e0-b948-08c1ecfea94b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForProceedsFromInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019fb4bc-6857-7522-9bc5-5408f0870dad" xlink:to="loc_us-gaap_PaymentsForProceedsFromInvestments_01a0331c-a315-72e0-b948-08c1ecfea94b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_01a13f77-acaf-7b18-9b91-004f6a688a00" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019fb4bc-6857-7522-9bc5-5408f0870dad" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_01a13f77-acaf-7b18-9b91-004f6a688a00" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019fb4bc-6857-702e-ae54-a43faa81943f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019fb4bc-6857-7522-9bc5-5408f0870dad" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019fb4bc-6857-702e-ae54-a43faa81943f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess_019fb4bc-6857-71bf-8ead-ad7989eb0302" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess_019fb4bc-6857-71bf-8ead-ad7989eb0302" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_019fb4bc-6857-708e-9d69-fe021cbb0078" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_019fb4bc-6857-708e-9d69-fe021cbb0078" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividends_019fb4bc-6857-7562-b5ca-587013dc2064" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfDividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_PaymentsOfDividends_019fb4bc-6857-7562-b5ca-587013dc2064" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019fb4bc-6857-73a9-a1e7-a1dc0608e3f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019fb4bc-6857-73a9-a1e7-a1dc0608e3f2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019fb4bc-6857-7658-8957-bf3b21f9a750" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019fb4bc-6857-7658-8957-bf3b21f9a750" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019fb4bc-6857-7a34-a3d5-762f4e59b77c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019fb4bc-6857-7a34-a3d5-762f4e59b77c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019fb4bc-6857-7bc9-8db6-e6f9186940ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019fb4bc-6857-7bc9-8db6-e6f9186940ea" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019fb4bc-6857-7fc6-b867-7f2ea6cbc41b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019fb4bc-6857-7159-b2a1-d990d7908ba1" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019fb4bc-6857-7fc6-b867-7f2ea6cbc41b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019fb4bc-6857-73e2-93bb-969e295aaf71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019fb4bc-6857-73e2-93bb-969e295aaf71" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019fb4bc-6857-799e-939a-f811ce7f67a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019fb4bc-6857-799e-939a-f811ce7f67a0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019fb4bc-6857-71aa-af75-d3cae4307ca4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d57-a3e2-eb8db7c1d98c" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019fb4bc-6857-71aa-af75-d3cae4307ca4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019fb4bc-6857-76b9-af67-500d55d774f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/ConsolidatedStatementsofShareholdersEquityUnaudited" xlink:type="simple" xlink:href="drs-20260930.xsd#ConsolidatedStatementsofShareholdersEquityUnaudited"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/ConsolidatedStatementsofShareholdersEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d15-a317-657dd07d7679" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019fb4bc-6857-7169-83cb-bbc77109a957" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d15-a317-657dd07d7679" xlink:to="loc_us-gaap_StatementTable_019fb4bc-6857-7169-83cb-bbc77109a957" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019fb4bc-6857-77d8-b000-d1e93c8acaf1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019fb4bc-6857-7169-83cb-bbc77109a957" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019fb4bc-6857-77d8-b000-d1e93c8acaf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d8-b000-d1e93c8acaf1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019fb4bc-6857-77d8-b000-d1e93c8acaf1" xlink:to="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d8-b000-d1e93c8acaf1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d1-90b3-585417b47aab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019fb4bc-6857-77d8-b000-d1e93c8acaf1" xlink:to="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d1-90b3-585417b47aab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019fb4bc-6857-7b24-823c-27fbba72044b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d1-90b3-585417b47aab" xlink:to="loc_us-gaap_CommonStockMember_019fb4bc-6857-7b24-823c-27fbba72044b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019fb4bc-6857-72ce-8fb1-da91231206ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d1-90b3-585417b47aab" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019fb4bc-6857-72ce-8fb1-da91231206ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019fb4bc-6857-767a-9bee-ad3576edc922" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d1-90b3-585417b47aab" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019fb4bc-6857-767a-9bee-ad3576edc922" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019fb4bc-6857-7b53-ad06-9351a00c7ead" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fb4bc-6857-77d1-90b3-585417b47aab" xlink:to="loc_us-gaap_RetainedEarningsMember_019fb4bc-6857-7b53-ad06-9351a00c7ead" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fb4bc-6857-7d15-a317-657dd07d7679" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019fb4bc-6857-79a3-9396-b3a54664d997" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019fb4bc-6857-79a3-9396-b3a54664d997" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019fb4bc-6857-732b-97ae-680793279c02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_StockholdersEquity_019fb4bc-6857-732b-97ae-680793279c02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019fb4bc-6857-7e24-b003-0f36635c22eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_019fb4bc-6857-7e24-b003-0f36635c22eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019fb4bc-6857-73a7-8731-7d7316747791" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019fb4bc-6857-73a7-8731-7d7316747791" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019fb4bc-6857-7aac-8621-7ff319010588" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019fb4bc-6857-7aac-8621-7ff319010588" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_01a03339-2e53-75fa-9d96-90258ec90ad2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_01a03339-2e53-75fa-9d96-90258ec90ad2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings_019fb4bc-6857-7b86-8c5b-e92a7756f211" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings_019fb4bc-6857-7b86-8c5b-e92a7756f211" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019fb4bc-6857-7e49-9d3f-34f85f8e3a57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fb4bc-6857-707b-bf9d-829527fcfcfe" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019fb4bc-6857-7e49-9d3f-34f85f8e3a57" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019fb4bc-6857-71b9-90ed-241c5a381b6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019fb4bc-6857-703f-a2c5-4b3b3fdc555a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#SummaryofSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_019fb4bc-68fc-7299-9c28-37899c377ff6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_019fb4bc-6857-7b8b-a740-6d28790ea3fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019fb4bc-68fc-7299-9c28-37899c377ff6" xlink:to="loc_us-gaap_ConcentrationRiskTable_019fb4bc-6857-7b8b-a740-6d28790ea3fb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_019fb4bc-6857-7ef8-9c60-224829e67f76" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_019fb4bc-6857-7b8b-a740-6d28790ea3fb" xlink:to="loc_srt_MajorCustomersAxis_019fb4bc-6857-7ef8-9c60-224829e67f76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019fb4bc-6857-7ef8-9c60-224829e67f76_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_019fb4bc-6857-7ef8-9c60-224829e67f76" xlink:to="loc_srt_NameOfMajorCustomerDomain_019fb4bc-6857-7ef8-9c60-224829e67f76_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019fb4bc-6857-784b-8c2f-fe5d1637601c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_019fb4bc-6857-7ef8-9c60-224829e67f76" xlink:to="loc_srt_NameOfMajorCustomerDomain_019fb4bc-6857-784b-8c2f-fe5d1637601c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_USDepartmentOfDefenseMember_019fb4bc-6857-70a2-b640-99de9abe8cac" xlink:href="drs-20260930.xsd#drs_USDepartmentOfDefenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019fb4bc-6857-784b-8c2f-fe5d1637601c" xlink:to="loc_drs_USDepartmentOfDefenseMember_019fb4bc-6857-70a2-b640-99de9abe8cac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_InternationalAndCommercialCustomersMember_019fb4bc-6857-744d-8980-3f8189735975" xlink:href="drs-20260930.xsd#drs_InternationalAndCommercialCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019fb4bc-6857-784b-8c2f-fe5d1637601c" xlink:to="loc_drs_InternationalAndCommercialCustomersMember_019fb4bc-6857-744d-8980-3f8189735975" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fb4bc-6857-7b40-9258-d8c2600a4136" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_019fb4bc-6857-7b8b-a740-6d28790ea3fb" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fb4bc-6857-7b40-9258-d8c2600a4136" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fb4bc-6857-7b40-9258-d8c2600a4136_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fb4bc-6857-7b40-9258-d8c2600a4136" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fb4bc-6857-7b40-9258-d8c2600a4136_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fb4bc-68fc-71c7-9b3f-d40be331f960" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fb4bc-6857-7b40-9258-d8c2600a4136" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fb4bc-68fc-71c7-9b3f-d40be331f960" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_019fb4bc-68fc-775e-9ac6-ba255c2270ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fb4bc-68fc-71c7-9b3f-d40be331f960" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_019fb4bc-68fc-775e-9ac6-ba255c2270ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019fb4bc-68fc-7bda-a79a-4b6b48997ea3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_019fb4bc-6857-7b8b-a740-6d28790ea3fb" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019fb4bc-68fc-7bda-a79a-4b6b48997ea3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019fb4bc-68fc-7bda-a79a-4b6b48997ea3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019fb4bc-68fc-7bda-a79a-4b6b48997ea3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019fb4bc-68fc-7bda-a79a-4b6b48997ea3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019fb4bc-68fc-7ca3-851e-dc2d0997fd5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019fb4bc-68fc-7bda-a79a-4b6b48997ea3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019fb4bc-68fc-7ca3-851e-dc2d0997fd5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractsConcentrationRiskMember_019fb4bc-68fc-7aeb-8587-e1ffe8161db5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GovernmentContractsConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019fb4bc-68fc-7ca3-851e-dc2d0997fd5f" xlink:to="loc_us-gaap_GovernmentContractsConcentrationRiskMember_019fb4bc-68fc-7aeb-8587-e1ffe8161db5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_019fb4bc-68fc-77ed-b277-ebb119ad0ab2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019fb4bc-68fc-7ca3-851e-dc2d0997fd5f" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_019fb4bc-68fc-77ed-b277-ebb119ad0ab2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_019fb4bc-68fc-7e2c-be8a-05a0af4359c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019fb4bc-68fc-7299-9c28-37899c377ff6" xlink:to="loc_us-gaap_NumberOfReportableSegments_019fb4bc-68fc-7e2c-be8a-05a0af4359c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019fb4bc-68fc-7b1c-b7bb-92ab4c771196" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019fb4bc-68fc-7299-9c28-37899c377ff6" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019fb4bc-68fc-7b1c-b7bb-92ab4c771196" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersScheduleofEstimateatCompletionAdjustmentsDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#RevenuefromContractswithCustomersScheduleofEstimateatCompletionAdjustmentsDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersScheduleofEstimateatCompletionAdjustmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateLineItems_019fb4bc-68fc-7985-a34b-f5daba55c3e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ChangeInAccountingEstimateLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfChangeInAccountingEstimateTable_019fb4bc-68fc-79cd-b4e5-e51847c5e279" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfChangeInAccountingEstimateTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_019fb4bc-68fc-7985-a34b-f5daba55c3e4" xlink:to="loc_us-gaap_ScheduleOfChangeInAccountingEstimateTable_019fb4bc-68fc-79cd-b4e5-e51847c5e279" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_019fb4bc-68fc-7f1f-b561-aef10bfd0f31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ChangeInAccountingEstimateByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfChangeInAccountingEstimateTable_019fb4bc-68fc-79cd-b4e5-e51847c5e279" xlink:to="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_019fb4bc-68fc-7f1f-b561-aef10bfd0f31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_019fb4bc-68fc-7f1f-b561-aef10bfd0f31_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_019fb4bc-68fc-7f1f-b561-aef10bfd0f31" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_019fb4bc-68fc-7f1f-b561-aef10bfd0f31_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_019fb4bc-68fc-704f-8170-4b737fbfdde6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_019fb4bc-68fc-7f1f-b561-aef10bfd0f31" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_019fb4bc-68fc-704f-8170-4b737fbfdde6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractsAccountedForUnderPercentageOfCompletionMember_019fb4bc-68fc-7f2a-9f42-efc498f81afe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractsAccountedForUnderPercentageOfCompletionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_019fb4bc-68fc-704f-8170-4b737fbfdde6" xlink:to="loc_us-gaap_ContractsAccountedForUnderPercentageOfCompletionMember_019fb4bc-68fc-7f2a-9f42-efc498f81afe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_RevenueAndOperatingIncomeLoss_019fb4bc-68fc-759e-a146-9d630c0d839e" xlink:href="drs-20260930.xsd#drs_RevenueAndOperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_019fb4bc-68fc-7985-a34b-f5daba55c3e4" xlink:to="loc_drs_RevenueAndOperatingIncomeLoss_019fb4bc-68fc-759e-a146-9d630c0d839e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_RevenueFromContractWithCustomerExcludingAssessedTaxPercent_019fb4bc-68fc-7bdf-aa9d-35357747d92a" xlink:href="drs-20260930.xsd#drs_RevenueFromContractWithCustomerExcludingAssessedTaxPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_019fb4bc-68fc-7985-a34b-f5daba55c3e4" xlink:to="loc_drs_RevenueFromContractWithCustomerExcludingAssessedTaxPercent_019fb4bc-68fc-7bdf-aa9d-35357747d92a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019fb4bc-68fc-7168-ac37-a29d3996d4ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_019fb4bc-68fc-7985-a34b-f5daba55c3e4" xlink:to="loc_us-gaap_NetIncomeLoss_019fb4bc-68fc-7168-ac37-a29d3996d4ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019fb4bc-68fc-79ca-8267-3a05d80fb926" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_019fb4bc-68fc-7985-a34b-f5daba55c3e4" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019fb4bc-68fc-79ca-8267-3a05d80fb926" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019fb4bc-68fc-74fd-9207-230f9242705e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019fb4bc-68fc-74fd-9207-230f9242705e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019fb4bc-68fc-767c-9432-b41c2639e9fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019fb4bc-68fc-74fd-9207-230f9242705e" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019fb4bc-68fc-767c-9432-b41c2639e9fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019fb4bc-68fc-74fd-9207-230f9242705e" xlink:to="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:to="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7f9a-b23b-1ef844fa74e2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:to="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7f9a-b23b-1ef844fa74e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_019fb4bc-68fc-7183-b53a-62bcfbae1df7" xlink:href="drs-20260930.xsd#drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7f9a-b23b-1ef844fa74e2" xlink:to="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_019fb4bc-68fc-7183-b53a-62bcfbae1df7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019fb4bc-68fc-728c-8d4e-2620e68d4269" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019fb4bc-68fc-728c-8d4e-2620e68d4269" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019fb4bc-68fc-7027-9319-04a3f7969416" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019fb4bc-68fc-7027-9319-04a3f7969416" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019fb4bc-68fc-7a85-9fe3-27cfcb3b38ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019fb4bc-68fc-7a85-9fe3-27cfcb3b38ad" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails_1" xlink:type="simple" xlink:href="drs-20260930.xsd#RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails_1"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019fb4bc-68fc-74fd-9207-230f9242705e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019fb4bc-68fc-74fd-9207-230f9242705e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019fb4bc-68fc-74fd-9207-230f9242705e" xlink:to="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:to="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7f9a-b23b-1ef844fa74e2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019fb4bc-68fc-7c92-9bf7-ffa5f3b88958" xlink:to="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7f9a-b23b-1ef844fa74e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_019fb4bc-68fc-7183-b53a-62bcfbae1df7" xlink:href="drs-20260930.xsd#drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019fb4bc-68fc-7f9a-b23b-1ef844fa74e2" xlink:to="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_019fb4bc-68fc-7183-b53a-62bcfbae1df7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019fb4bc-68fc-728c-8d4e-2620e68d4269" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019fb4bc-68fc-728c-8d4e-2620e68d4269" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019fb4bc-68fc-7027-9319-04a3f7969416" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_019fb4bc-68fc-7027-9319-04a3f7969416" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019fb4bc-68fc-7a85-9fe3-27cfcb3b38ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019fb4bc-68fc-7cb4-a756-474a6a440736" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019fb4bc-68fc-7a85-9fe3-27cfcb3b38ad" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersScheduleofDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#RevenuefromContractswithCustomersScheduleofDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersScheduleofDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019fb4bc-68fc-718c-bfba-d1b0b9014523" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019fb4bc-68fc-7689-80cd-583653dba389" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019fb4bc-68fc-718c-bfba-d1b0b9014523" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019fb4bc-68fc-7689-80cd-583653dba389" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fc-7a89-86a3-b80f4e9c2236" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019fb4bc-68fc-7689-80cd-583653dba389" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fc-7a89-86a3-b80f4e9c2236" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fc-7a89-86a3-b80f4e9c2236_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fc-7a89-86a3-b80f4e9c2236" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fc-7a89-86a3-b80f4e9c2236_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fc-7e15-a527-6ada4486283b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fc-7a89-86a3-b80f4e9c2236" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fc-7e15-a527-6ada4486283b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fc-7a12-bc62-55f26ad397d2" xlink:href="drs-20260930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fc-7e15-a527-6ada4486283b" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fc-7a12-bc62-55f26ad397d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fc-79d3-8bb2-c2f15e85c4d0" xlink:href="drs-20260930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fc-7e15-a527-6ada4486283b" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fc-79d3-8bb2-c2f15e85c4d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019fb4bc-68fc-75e8-be18-e510df1566af" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019fb4bc-68fc-7689-80cd-583653dba389" xlink:to="loc_srt_StatementGeographicalAxis_019fb4bc-68fc-75e8-be18-e510df1566af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019fb4bc-68fc-75e8-be18-e510df1566af_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019fb4bc-68fc-75e8-be18-e510df1566af" xlink:to="loc_srt_SegmentGeographicalDomain_019fb4bc-68fc-75e8-be18-e510df1566af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019fb4bc-68fc-7f7b-aacc-085118035590" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019fb4bc-68fc-75e8-be18-e510df1566af" xlink:to="loc_srt_SegmentGeographicalDomain_019fb4bc-68fc-7f7b-aacc-085118035590" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019fb4bc-68fc-7686-afd0-c0f364f0bfde" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019fb4bc-68fc-7f7b-aacc-085118035590" xlink:to="loc_country_US_019fb4bc-68fc-7686-afd0-c0f364f0bfde" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019fb4bc-68fc-7358-a4e2-e87c4ca2db86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019fb4bc-68fc-7f7b-aacc-085118035590" xlink:to="loc_us-gaap_NonUsMember_019fb4bc-68fc-7358-a4e2-e87c4ca2db86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019fb4bc-68fc-7f5f-a599-8b40e686802f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019fb4bc-68fc-7689-80cd-583653dba389" xlink:to="loc_srt_ConsolidationItemsAxis_019fb4bc-68fc-7f5f-a599-8b40e686802f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fc-7f5f-a599-8b40e686802f_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fc-7f5f-a599-8b40e686802f" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fc-7f5f-a599-8b40e686802f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fc-77af-891c-c35bf1486b39" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fc-7f5f-a599-8b40e686802f" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fc-77af-891c-c35bf1486b39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_019fb4bc-68fc-7cc2-b697-4d9f2d81352a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019fb4bc-68fc-77af-891c-c35bf1486b39" xlink:to="loc_us-gaap_IntersegmentEliminationMember_019fb4bc-68fc-7cc2-b697-4d9f2d81352a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019fb4bc-68fc-7b2d-9b41-4dac29436ef6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019fb4bc-68fc-77af-891c-c35bf1486b39" xlink:to="loc_us-gaap_OperatingSegmentsMember_019fb4bc-68fc-7b2d-9b41-4dac29436ef6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelAxis_019fb4bc-68fc-7619-bfb5-15d6c8891c51" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerSalesChannelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019fb4bc-68fc-7689-80cd-583653dba389" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelAxis_019fb4bc-68fc-7619-bfb5-15d6c8891c51" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_019fb4bc-68fc-7619-bfb5-15d6c8891c51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_019fb4bc-68fc-7619-bfb5-15d6c8891c51" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_019fb4bc-68fc-7619-bfb5-15d6c8891c51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_019fb4bc-68fc-7ee7-b070-5a99c554dedf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_019fb4bc-68fc-7619-bfb5-15d6c8891c51" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_019fb4bc-68fc-7ee7-b070-5a99c554dedf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelDirectlyToConsumerMember_019fb4bc-68fc-7407-8cde-39ce9026dbeb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesChannelDirectlyToConsumerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_019fb4bc-68fc-7ee7-b070-5a99c554dedf" xlink:to="loc_us-gaap_SalesChannelDirectlyToConsumerMember_019fb4bc-68fc-7407-8cde-39ce9026dbeb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelThroughIntermediaryMember_019fb4bc-68fc-7566-a918-61e9fb65b203" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesChannelThroughIntermediaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_019fb4bc-68fc-7ee7-b070-5a99c554dedf" xlink:to="loc_us-gaap_SalesChannelThroughIntermediaryMember_019fb4bc-68fc-7566-a918-61e9fb65b203" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019fb4bc-68fc-795b-b0d7-bfe1018c1989" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerBasisOfPricingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019fb4bc-68fc-7689-80cd-583653dba389" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019fb4bc-68fc-795b-b0d7-bfe1018c1989" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019fb4bc-68fc-795b-b0d7-bfe1018c1989_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019fb4bc-68fc-795b-b0d7-bfe1018c1989" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019fb4bc-68fc-795b-b0d7-bfe1018c1989_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019fb4bc-68fc-7863-be4e-57f00253da42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_019fb4bc-68fc-795b-b0d7-bfe1018c1989" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019fb4bc-68fc-7863-be4e-57f00253da42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedPriceContractMember_019fb4bc-68fc-70f2-adf0-23f7464bd670" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedPriceContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019fb4bc-68fc-7863-be4e-57f00253da42" xlink:to="loc_us-gaap_FixedPriceContractMember_019fb4bc-68fc-70f2-adf0-23f7464bd670" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimeAndMaterialsContractMember_019fb4bc-68fc-7710-b0be-fb31e55aad4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TimeAndMaterialsContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_019fb4bc-68fc-7863-be4e-57f00253da42" xlink:to="loc_us-gaap_TimeAndMaterialsContractMember_019fb4bc-68fc-7710-b0be-fb31e55aad4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fc-7f15-8b38-a55138e57f7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019fb4bc-68fc-718c-bfba-d1b0b9014523" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fc-7f15-8b38-a55138e57f7f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019fb4bc-68fc-7235-8e27-3b520e2c8408" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019fb4bc-68fc-79ed-bc4c-76c0106c032d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019fb4bc-68fc-7235-8e27-3b520e2c8408" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019fb4bc-68fc-79ed-bc4c-76c0106c032d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb4bc-68fc-7837-8630-19fa5de36a86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019fb4bc-68fc-79ed-bc4c-76c0106c032d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb4bc-68fc-7837-8630-19fa5de36a86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb4bc-68fc-7837-8630-19fa5de36a86_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb4bc-68fc-7837-8630-19fa5de36a86" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb4bc-68fc-7837-8630-19fa5de36a86_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb4bc-68fc-7080-aa0a-7e98e7ac35e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb4bc-68fc-7837-8630-19fa5de36a86" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb4bc-68fc-7080-aa0a-7e98e7ac35e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandBuildingsAndImprovementsMember_019fb4bc-68fc-771a-9bde-a85a9504b697" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LandBuildingsAndImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb4bc-68fc-7080-aa0a-7e98e7ac35e3" xlink:to="loc_us-gaap_LandBuildingsAndImprovementsMember_019fb4bc-68fc-771a-9bde-a85a9504b697" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_019fb4bc-68fc-7ed5-a10a-d91309009b5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb4bc-68fc-7080-aa0a-7e98e7ac35e3" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_019fb4bc-68fc-7ed5-a10a-d91309009b5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_EquipmentAndOtherCapitalizedPropertyPlantAndEquipmentMember_019fb4bc-68fc-72f7-a88f-fc40127ee7f1" xlink:href="drs-20260930.xsd#drs_EquipmentAndOtherCapitalizedPropertyPlantAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb4bc-68fc-7080-aa0a-7e98e7ac35e3" xlink:to="loc_drs_EquipmentAndOtherCapitalizedPropertyPlantAndEquipmentMember_019fb4bc-68fc-72f7-a88f-fc40127ee7f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019fb4bc-68fc-7af7-b99d-0ac4716b0a31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019fb4bc-68fc-7235-8e27-3b520e2c8408" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019fb4bc-68fc-7af7-b99d-0ac4716b0a31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019fb4bc-68fc-7c1f-a838-1429a4f8a3c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019fb4bc-68fc-7235-8e27-3b520e2c8408" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019fb4bc-68fc-7c1f-a838-1429a4f8a3c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019fb4bc-68fc-7cda-90d1-3daeb9143df8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019fb4bc-68fc-7235-8e27-3b520e2c8408" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019fb4bc-68fc-7cda-90d1-3daeb9143df8" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/IntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#IntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/IntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019fb4bc-68fd-70bd-8516-988b33b98f42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019fb4bc-68fd-7bae-b713-7f8228570f9e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019fb4bc-68fd-70bd-8516-988b33b98f42" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019fb4bc-68fd-7bae-b713-7f8228570f9e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019fb4bc-68fd-7c37-8730-9e19468f1cd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019fb4bc-68fd-7bae-b713-7f8228570f9e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019fb4bc-68fd-7c37-8730-9e19468f1cd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019fb4bc-68fd-7c37-8730-9e19468f1cd8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019fb4bc-68fd-7c37-8730-9e19468f1cd8" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019fb4bc-68fd-7c37-8730-9e19468f1cd8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019fb4bc-68fd-7707-ba6d-8de91c806353" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019fb4bc-68fd-7c37-8730-9e19468f1cd8" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019fb4bc-68fd-7707-ba6d-8de91c806353" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AcquiredIntangibleAssetsMember_019fb4bc-68fd-7fd1-9b24-55ca3d93961b" xlink:href="drs-20260930.xsd#drs_AcquiredIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019fb4bc-68fd-7707-ba6d-8de91c806353" xlink:to="loc_drs_AcquiredIntangibleAssetsMember_019fb4bc-68fd-7fd1-9b24-55ca3d93961b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_PatentsAndLicenseMember_019fb4bc-68fd-7629-b91a-7393d112f1ed" xlink:href="drs-20260930.xsd#drs_PatentsAndLicenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019fb4bc-68fd-7707-ba6d-8de91c806353" xlink:to="loc_drs_PatentsAndLicenseMember_019fb4bc-68fd-7629-b91a-7393d112f1ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019fb4bc-68fd-7ddc-992e-440ff944ad12" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019fb4bc-68fd-70bd-8516-988b33b98f42" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019fb4bc-68fd-7ddc-992e-440ff944ad12" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019fb4bc-68fd-73de-b293-dc2af1361768" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019fb4bc-68fd-70bd-8516-988b33b98f42" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019fb4bc-68fd-73de-b293-dc2af1361768" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019fb4bc-68fd-7223-aec3-ae07f6cb3228" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019fb4bc-68fd-70bd-8516-988b33b98f42" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019fb4bc-68fd-7223-aec3-ae07f6cb3228" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/DebtScheduleofLongTermDebtDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#DebtScheduleofLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/DebtScheduleofLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-723d-923a-f860f8c7847e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-723d-923a-f860f8c7847e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-75c2-9392-78c52873aa09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-723d-923a-f860f8c7847e" xlink:to="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-75c2-9392-78c52873aa09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-75c2-9392-78c52873aa09_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-75c2-9392-78c52873aa09" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-75c2-9392-78c52873aa09_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-73f3-a72c-b7a54ea3a0ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-75c2-9392-78c52873aa09" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-73f3-a72c-b7a54ea3a0ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2022CreditAgreementTermLoanAMember_019fb4bc-68fd-75de-aabb-df8e372a93f8" xlink:href="drs-20260930.xsd#drs_A2022CreditAgreementTermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-73f3-a72c-b7a54ea3a0ef" xlink:to="loc_drs_A2022CreditAgreementTermLoanAMember_019fb4bc-68fd-75de-aabb-df8e372a93f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-751d-a18c-4ac458d5ad70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-723d-923a-f860f8c7847e" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-751d-a18c-4ac458d5ad70" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-751d-a18c-4ac458d5ad70_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-751d-a18c-4ac458d5ad70" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-751d-a18c-4ac458d5ad70_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-71ce-8952-374eeda3054d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-751d-a18c-4ac458d5ad70" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-71ce-8952-374eeda3054d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_019fb4bc-68fd-7872-9268-203161c32702" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-71ce-8952-374eeda3054d" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_019fb4bc-68fd-7872-9268-203161c32702" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019fb4bc-68fd-74c1-b22e-4749b117eca1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019fb4bc-68fd-74c1-b22e-4749b117eca1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_FinanceLeaseLiabilityAndOtherLiability_019fb4bc-68fd-7bf3-a636-46fc953f1cf3" xlink:href="drs-20260930.xsd#drs_FinanceLeaseLiabilityAndOtherLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_drs_FinanceLeaseLiabilityAndOtherLiability_019fb4bc-68fd-7bf3-a636-46fc953f1cf3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_019fb4bc-68fd-728c-86fa-26ea581f10f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_us-gaap_ShortTermBorrowings_019fb4bc-68fd-728c-86fa-26ea581f10f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_DebtAndFinanceLeaseObligationsGross_019fb4bc-68fd-7156-aa23-37bac6ea3abb" xlink:href="drs-20260930.xsd#drs_DebtAndFinanceLeaseObligationsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_drs_DebtAndFinanceLeaseObligationsGross_019fb4bc-68fd-7156-aa23-37bac6ea3abb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019fb4bc-68fd-7a2b-963e-981b65ef775a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019fb4bc-68fd-7a2b-963e-981b65ef775a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndCapitalLeaseObligations_019fb4bc-68fd-768b-bb37-6c458654bc08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_us-gaap_DebtAndCapitalLeaseObligations_019fb4bc-68fd-768b-bb37-6c458654bc08" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_019fb4bc-68fd-78e7-82b6-2e1bcd18c71e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_us-gaap_DebtCurrent_019fb4bc-68fd-78e7-82b6-2e1bcd18c71e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019fb4bc-68fd-7d0c-854f-a17f87246d87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7d07-9eb8-e0ea51188dc3" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019fb4bc-68fd-7d0c-854f-a17f87246d87" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#DebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/DebtNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-7f9d-9fe3-1382a956317c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-7f9d-9fe3-1382a956317c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-7f7c-bbc4-fd78fcffcfd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-7f9d-9fe3-1382a956317c" xlink:to="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-7f7c-bbc4-fd78fcffcfd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-7f7c-bbc4-fd78fcffcfd6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-7f7c-bbc4-fd78fcffcfd6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-7f7c-bbc4-fd78fcffcfd6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-7969-824c-3d75bd3a6014" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fb4bc-68fd-7f7c-bbc4-fd78fcffcfd6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-7969-824c-3d75bd3a6014" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2022CreditAgreementMember_019fb4bc-68fd-7db4-9868-4f9cd8100609" xlink:href="drs-20260930.xsd#drs_A2022CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-7969-824c-3d75bd3a6014" xlink:to="loc_drs_A2022CreditAgreementMember_019fb4bc-68fd-7db4-9868-4f9cd8100609" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2022CreditAgreementTermLoanAMember_019fb4bc-68fd-7c6c-900a-8b2a34ca9f43" xlink:href="drs-20260930.xsd#drs_A2022CreditAgreementTermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_drs_A2022CreditAgreementMember_019fb4bc-68fd-7db4-9868-4f9cd8100609" xlink:to="loc_drs_A2022CreditAgreementTermLoanAMember_019fb4bc-68fd-7c6c-900a-8b2a34ca9f43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2022RevolvingCreditFacilityMember_019fb4bc-68fd-7dc8-a47b-e9732370c074" xlink:href="drs-20260930.xsd#drs_A2022RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_drs_A2022CreditAgreementMember_019fb4bc-68fd-7db4-9868-4f9cd8100609" xlink:to="loc_drs_A2022RevolvingCreditFacilityMember_019fb4bc-68fd-7dc8-a47b-e9732370c074" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2026RevolvingCreditFacilityMember_019fb4bc-68fd-71b1-acf6-285c6551ce58" xlink:href="drs-20260930.xsd#drs_A2026RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-7969-824c-3d75bd3a6014" xlink:to="loc_drs_A2026RevolvingCreditFacilityMember_019fb4bc-68fd-71b1-acf6-285c6551ce58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_FinancialInstitutionCreditFacilitiesMember_019fb4bc-68fd-7b39-a97f-48b1b306806a" xlink:href="drs-20260930.xsd#drs_FinancialInstitutionCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fb4bc-68fd-7969-824c-3d75bd3a6014" xlink:to="loc_drs_FinancialInstitutionCreditFacilitiesMember_019fb4bc-68fd-7b39-a97f-48b1b306806a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-714b-8b57-2c25ce20dc98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-7f9d-9fe3-1382a956317c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-714b-8b57-2c25ce20dc98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-714b-8b57-2c25ce20dc98_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-714b-8b57-2c25ce20dc98" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-714b-8b57-2c25ce20dc98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-7416-bbca-8085d37ba42b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb4bc-68fd-714b-8b57-2c25ce20dc98" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-7416-bbca-8085d37ba42b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_019fb4bc-68fd-7c38-823e-d1dff495544c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-7416-bbca-8085d37ba42b" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_019fb4bc-68fd-7c38-823e-d1dff495544c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_019fb4bc-68fd-745b-aae3-ebfc8fc872b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NotesPayableOtherPayablesMember_019fb4bc-68fd-7c38-823e-d1dff495544c" xlink:to="loc_us-gaap_LetterOfCreditMember_019fb4bc-68fd-745b-aae3-ebfc8fc872b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019fb4bc-68fd-72e0-952b-b2c7d2960f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019fb4bc-68fd-7416-bbca-8085d37ba42b" xlink:to="loc_us-gaap_LineOfCreditMember_019fb4bc-68fd-72e0-952b-b2c7d2960f1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019fb4bc-68fd-76ab-a7ac-7860c86a4291" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fb4bc-68fd-7f9d-9fe3-1382a956317c" xlink:to="loc_srt_RangeAxis_019fb4bc-68fd-76ab-a7ac-7860c86a4291" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019fb4bc-68fd-76ab-a7ac-7860c86a4291_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019fb4bc-68fd-76ab-a7ac-7860c86a4291" xlink:to="loc_srt_RangeMember_019fb4bc-68fd-76ab-a7ac-7860c86a4291_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019fb4bc-68fd-79e1-b94b-3a7c6611e58c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019fb4bc-68fd-76ab-a7ac-7860c86a4291" xlink:to="loc_srt_RangeMember_019fb4bc-68fd-79e1-b94b-3a7c6611e58c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019fb4bc-68fd-7a31-91e9-0fa3c0601072" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019fb4bc-68fd-79e1-b94b-3a7c6611e58c" xlink:to="loc_srt_MinimumMember_019fb4bc-68fd-7a31-91e9-0fa3c0601072" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019fb4bc-68fd-7e65-8a0d-e43384a7a0da" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019fb4bc-68fd-79e1-b94b-3a7c6611e58c" xlink:to="loc_srt_MaximumMember_019fb4bc-68fd-7e65-8a0d-e43384a7a0da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019fb4bc-68fd-71ed-8151-0fb150afed85" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019fb4bc-68fd-71ed-8151-0fb150afed85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019fb4bc-68fd-7d13-b834-483f54f06101" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019fb4bc-68fd-7d13-b834-483f54f06101" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019fb4bc-68fd-7f24-85d8-23a37fc71012" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_LongTermDebtFairValue_019fb4bc-68fd-7f24-85d8-23a37fc71012" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfDebt_019fb4bc-68fd-7150-b677-b2c79ae857dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_RepaymentsOfDebt_019fb4bc-68fd-7150-b677-b2c79ae857dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_019fb4bc-68fd-7c45-8c9e-20ee24c11d13" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_LineOfCredit_019fb4bc-68fd-7c45-8c9e-20ee24c11d13" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019fb4bc-68fd-7c9f-b654-fd50bcc8cf4c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019fb4bc-68fd-7c9f-b654-fd50bcc8cf4c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019fb4bc-68fd-7a2d-b230-2840cd83e72d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019fb4bc-68fd-7a2d-b230-2840cd83e72d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_019fb4bc-68fd-79ed-914d-39e9c492e886" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_019fb4bc-68fd-79ed-914d-39e9c492e886" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_019fb4bc-68fd-712c-8bb1-aacd1dcbacc1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fb4bc-68fd-7596-ad93-55eb475ec21f" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_019fb4bc-68fd-712c-8bb1-aacd1dcbacc1" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/EarningsPerShareEPSStockRepurchasesandDividendsNarrativeDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#EarningsPerShareEPSStockRepurchasesandDividendsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/EarningsPerShareEPSStockRepurchasesandDividendsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramLineItems_019fb4bc-68fd-7d4d-903e-430641fdd06d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramTable_019fb4bc-68fd-7dba-aa96-74bfbc6cdad3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_019fb4bc-68fd-7d4d-903e-430641fdd06d" xlink:to="loc_srt_ShareRepurchaseProgramTable_019fb4bc-68fd-7dba-aa96-74bfbc6cdad3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019fb4bc-68fd-7b7a-b842-7ed9a9d98e9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ShareRepurchaseProgramTable_019fb4bc-68fd-7dba-aa96-74bfbc6cdad3" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019fb4bc-68fd-7b7a-b842-7ed9a9d98e9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019fb4bc-68fd-7b7a-b842-7ed9a9d98e9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019fb4bc-68fd-7b7a-b842-7ed9a9d98e9b" xlink:to="loc_us-gaap_ClassOfStockDomain_019fb4bc-68fd-7b7a-b842-7ed9a9d98e9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019fb4bc-68fd-7376-9b34-881ee8e7bb19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019fb4bc-68fd-7b7a-b842-7ed9a9d98e9b" xlink:to="loc_us-gaap_ClassOfStockDomain_019fb4bc-68fd-7376-9b34-881ee8e7bb19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019fb4bc-68fd-7860-9cb9-5bb954ca3b5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019fb4bc-68fd-7376-9b34-881ee8e7bb19" xlink:to="loc_us-gaap_CommonClassAMember_019fb4bc-68fd-7860-9cb9-5bb954ca3b5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019fb4bc-68fd-799f-b224-cba75e9f7bea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ShareRepurchaseProgramTable_019fb4bc-68fd-7dba-aa96-74bfbc6cdad3" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019fb4bc-68fd-799f-b224-cba75e9f7bea" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fb4bc-68fd-799f-b224-cba75e9f7bea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fb4bc-68fd-799f-b224-cba75e9f7bea" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fb4bc-68fd-799f-b224-cba75e9f7bea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fb4bc-68fd-7859-8b76-e06585154c14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fb4bc-68fd-799f-b224-cba75e9f7bea" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fb4bc-68fd-7859-8b76-e06585154c14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019fb4bc-68fd-74bd-ad10-c496db580fa4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019fb4bc-68fd-7859-8b76-e06585154c14" xlink:to="loc_us-gaap_SubsequentEventMember_019fb4bc-68fd-74bd-ad10-c496db580fa4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019fb4bc-68fd-73a4-bd64-2f8f5bb6c2f7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_019fb4bc-68fd-7d4d-903e-430641fdd06d" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019fb4bc-68fd-73a4-bd64-2f8f5bb6c2f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019fb4bc-68fd-7bb4-a61f-f11b614b92a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_019fb4bc-68fd-7d4d-903e-430641fdd06d" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019fb4bc-68fd-7bb4-a61f-f11b614b92a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019fb4bc-68fd-77b1-a2d9-8e474911c81d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_019fb4bc-68fd-7d4d-903e-430641fdd06d" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019fb4bc-68fd-77b1-a2d9-8e474911c81d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#RelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RelatedPartyTransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fb4bc-68fd-7c83-821d-9cca25c16c5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fb4bc-68fd-7c83-821d-9cca25c16c5f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-68fd-7605-beca-8cf2a5993973" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fb4bc-68fd-7c83-821d-9cca25c16c5f" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-68fd-7605-beca-8cf2a5993973" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fb4bc-68fd-7605-beca-8cf2a5993973_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-68fd-7605-beca-8cf2a5993973" xlink:to="loc_us-gaap_RelatedPartyDomain_019fb4bc-68fd-7605-beca-8cf2a5993973_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fb4bc-68fd-77ed-8d33-9afce2c1fd22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb4bc-68fd-7605-beca-8cf2a5993973" xlink:to="loc_us-gaap_RelatedPartyDomain_019fb4bc-68fd-77ed-8d33-9afce2c1fd22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019fb4bc-68fd-79d7-98ee-9cf857dc55ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fb4bc-68fd-77ed-8d33-9afce2c1fd22" xlink:to="loc_us-gaap_RelatedPartyMember_019fb4bc-68fd-79d7-98ee-9cf857dc55ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019fb4bc-68fd-759f-b225-45cbe0af3bf4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fb4bc-68fd-7c83-821d-9cca25c16c5f" xlink:to="loc_srt_CounterpartyNameAxis_019fb4bc-68fd-759f-b225-45cbe0af3bf4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fb4bc-68fd-759f-b225-45cbe0af3bf4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019fb4bc-68fd-759f-b225-45cbe0af3bf4" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fb4bc-68fd-759f-b225-45cbe0af3bf4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fb4bc-68fd-7e6e-b125-834833c5f612" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019fb4bc-68fd-759f-b225-45cbe0af3bf4" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fb4bc-68fd-7e6e-b125-834833c5f612" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_LeonardoSpAMember_019fb4bc-68fd-7094-a163-bb435ce2ff58" xlink:href="drs-20260930.xsd#drs_LeonardoSpAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fb4bc-68fd-7e6e-b125-834833c5f612" xlink:to="loc_drs_LeonardoSpAMember_019fb4bc-68fd-7094-a163-bb435ce2ff58" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_UnnamedPrivateCompanyMember_019fb4bc-68fd-749b-a726-dcaa366caca1" xlink:href="drs-20260930.xsd#drs_UnnamedPrivateCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fb4bc-68fd-7e6e-b125-834833c5f612" xlink:to="loc_drs_UnnamedPrivateCompanyMember_019fb4bc-68fd-749b-a726-dcaa366caca1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fd-78b3-9c38-12dba965c421" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fd-78b3-9c38-12dba965c421" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_019fb4bc-68fd-7e7c-abda-a7bc5ce670ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_us-gaap_CostOfRevenue_019fb4bc-68fd-7e7c-abda-a7bc5ce670ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019fb4bc-68fd-7582-869e-14104d019240" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019fb4bc-68fd-7582-869e-14104d019240" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019fb4bc-68fd-7001-b5a1-6ffb080b1fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_us-gaap_AccountsPayableCurrent_019fb4bc-68fd-7001-b5a1-6ffb080b1fdd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019fb4bc-68fd-7208-9565-357f31aa6c2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019fb4bc-68fd-7208-9565-357f31aa6c2d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_019fb4bc-68fd-7448-b2f3-8aa3178b5d2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Investments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_us-gaap_Investments_019fb4bc-68fd-7448-b2f3-8aa3178b5d2c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_NumberOfBoardSeats_019fb4bc-68fd-7475-ba34-31e608073c4f" xlink:href="drs-20260930.xsd#drs_NumberOfBoardSeats"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fb4bc-68fd-72c2-89ac-b3c5ceac23c5" xlink:to="loc_drs_NumberOfBoardSeats_019fb4bc-68fd-7475-ba34-31e608073c4f" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationScheduleofRevenuesExpensesandOperatingEarningsbySegmentandReconciliationtoEarningsbeforeTaxesDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#SegmentInformationScheduleofRevenuesExpensesandOperatingEarningsbySegmentandReconciliationtoEarningsbeforeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationScheduleofRevenuesExpensesandOperatingEarningsbySegmentandReconciliationtoEarningsbeforeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7a5a-982f-bbb26e4448d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7a5a-982f-bbb26e4448d1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-764c-86d0-dcd94330ba53" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7a5a-982f-bbb26e4448d1" xlink:to="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-764c-86d0-dcd94330ba53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-764c-86d0-dcd94330ba53_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-764c-86d0-dcd94330ba53" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-764c-86d0-dcd94330ba53_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-742e-bc1a-cf9947f0c579" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-764c-86d0-dcd94330ba53" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-742e-bc1a-cf9947f0c579" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019fb4bc-68fd-7b5f-9fe5-4e1c75928a9a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-742e-bc1a-cf9947f0c579" xlink:to="loc_us-gaap_OperatingSegmentsMember_019fb4bc-68fd-7b5f-9fe5-4e1c75928a9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_CorporateAndEliminationsMember_019fb4bc-68fd-7de6-89a1-34dda938dd61" xlink:href="drs-20260930.xsd#drs_CorporateAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-742e-bc1a-cf9947f0c579" xlink:to="loc_drs_CorporateAndEliminationsMember_019fb4bc-68fd-7de6-89a1-34dda938dd61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-7845-9626-2f55962aa3b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7a5a-982f-bbb26e4448d1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-7845-9626-2f55962aa3b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7845-9626-2f55962aa3b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-7845-9626-2f55962aa3b4" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7845-9626-2f55962aa3b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-732c-ab15-5fba3d89f126" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-7845-9626-2f55962aa3b4" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-732c-ab15-5fba3d89f126" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-7ff0-ac04-3a0e4d615288" xlink:href="drs-20260930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-732c-ab15-5fba3d89f126" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-7ff0-ac04-3a0e4d615288" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-7c39-8ba5-e2f6220e7892" xlink:href="drs-20260930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-732c-ab15-5fba3d89f126" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-7c39-8ba5-e2f6220e7892" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fd-71a9-adb1-c3d855ceac78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fd-71a9-adb1-c3d855ceac78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_019fb4bc-68fd-7a59-a5ef-5b9e74977f2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_CostOfRevenue_019fb4bc-68fd-7a59-a5ef-5b9e74977f2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019fb4bc-68fd-70ae-989b-e09e96892b78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019fb4bc-68fd-70ae-989b-e09e96892b78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019fb4bc-68fd-758d-82fe-2ced1de5e8b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019fb4bc-68fd-758d-82fe-2ced1de5e8b7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019fb4bc-68fd-76dc-940b-f8a311994aed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019fb4bc-68fd-76dc-940b-f8a311994aed" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_01a0ecf2-a577-76f4-a87e-33b47a9e07d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingOtherItemAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_01a0ecf2-a577-76f4-a87e-33b47a9e07d9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019fb4bc-68fd-7016-9b35-91e37598140a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_OperatingIncomeLoss_019fb4bc-68fd-7016-9b35-91e37598140a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019fb4bc-68fd-7fa7-94b4-264a5a4e395c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019fb4bc-68fd-7fa7-94b4-264a5a4e395c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019fb4bc-68fd-784d-8801-48b9247376b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019fb4bc-68fd-784d-8801-48b9247376b7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019fb4bc-68fd-7e8a-847b-e6c50d3cedf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7c9f-aaf4-f78060aff75d" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019fb4bc-68fd-7e8a-847b-e6c50d3cedf3" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationScheduleofRevenuesandIntersegmentRevenuesDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#SegmentInformationScheduleofRevenuesandIntersegmentRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationScheduleofRevenuesandIntersegmentRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-732f-8fc0-ca9c773a9ccd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-796a-86c4-f15d2ed01a2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-732f-8fc0-ca9c773a9ccd" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-796a-86c4-f15d2ed01a2b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-75b0-9677-f5360f806612" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-796a-86c4-f15d2ed01a2b" xlink:to="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-75b0-9677-f5360f806612" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-75b0-9677-f5360f806612_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-75b0-9677-f5360f806612" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-75b0-9677-f5360f806612_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7e0b-aca6-f125026cc584" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-75b0-9677-f5360f806612" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7e0b-aca6-f125026cc584" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_019fb4bc-68fd-7c2c-9f5b-1b9f11c85f28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7e0b-aca6-f125026cc584" xlink:to="loc_us-gaap_IntersegmentEliminationMember_019fb4bc-68fd-7c2c-9f5b-1b9f11c85f28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-72ca-b8bb-a1f29626852c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-796a-86c4-f15d2ed01a2b" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-72ca-b8bb-a1f29626852c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-72ca-b8bb-a1f29626852c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-72ca-b8bb-a1f29626852c" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-72ca-b8bb-a1f29626852c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7ccc-84c4-fc0027a7545f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-72ca-b8bb-a1f29626852c" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7ccc-84c4-fc0027a7545f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-7cc8-a677-3976281515b7" xlink:href="drs-20260930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7ccc-84c4-fc0027a7545f" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-7cc8-a677-3976281515b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-712e-95aa-c86aaca8732b" xlink:href="drs-20260930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7ccc-84c4-fc0027a7545f" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-712e-95aa-c86aaca8732b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fd-7a0a-83e4-172fb290caf6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-732f-8fc0-ca9c773a9ccd" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019fb4bc-68fd-7a0a-83e4-172fb290caf6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationScheduleofDepreciationbySegmentDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#SegmentInformationScheduleofDepreciationbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationScheduleofDepreciationbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7804-ab36-c1f815b0eb6a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7419-a551-a487343cb001" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7804-ab36-c1f815b0eb6a" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7419-a551-a487343cb001" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-70e7-84b6-3c4cfde3ec14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7419-a551-a487343cb001" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-70e7-84b6-3c4cfde3ec14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-70e7-84b6-3c4cfde3ec14_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-70e7-84b6-3c4cfde3ec14" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-70e7-84b6-3c4cfde3ec14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7422-ad91-853f20099616" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-70e7-84b6-3c4cfde3ec14" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7422-ad91-853f20099616" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-7b55-86ce-39118449ffef" xlink:href="drs-20260930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7422-ad91-853f20099616" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-7b55-86ce-39118449ffef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-7f00-8003-06d542111959" xlink:href="drs-20260930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7422-ad91-853f20099616" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-7f00-8003-06d542111959" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_019fb4bc-68fd-7c5d-a533-0a7e06c35f0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7804-ab36-c1f815b0eb6a" xlink:to="loc_us-gaap_Depreciation_019fb4bc-68fd-7c5d-a533-0a7e06c35f0a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationScheduleofTotalAssetsbySegmentDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#SegmentInformationScheduleofTotalAssetsbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationScheduleofTotalAssetsbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7eb4-8f52-db2c66213b36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7746-8673-df9bbf147bcf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7eb4-8f52-db2c66213b36" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7746-8673-df9bbf147bcf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-7c67-9213-292ef8a80c36" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7746-8673-df9bbf147bcf" xlink:to="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-7c67-9213-292ef8a80c36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7c67-9213-292ef8a80c36_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-7c67-9213-292ef8a80c36" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7c67-9213-292ef8a80c36_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7d97-a23b-54acea57dde1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019fb4bc-68fd-7c67-9213-292ef8a80c36" xlink:to="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7d97-a23b-54acea57dde1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019fb4bc-68fd-7eb2-b8a2-6d7fc2d00fcc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7d97-a23b-54acea57dde1" xlink:to="loc_us-gaap_OperatingSegmentsMember_019fb4bc-68fd-7eb2-b8a2-6d7fc2d00fcc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_CorporateAndEliminationsMember_019fb4bc-68fd-7268-af39-dd5265b2e7ea" xlink:href="drs-20260930.xsd#drs_CorporateAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019fb4bc-68fd-7d97-a23b-54acea57dde1" xlink:to="loc_drs_CorporateAndEliminationsMember_019fb4bc-68fd-7268-af39-dd5265b2e7ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-737e-9f96-0642f7bff454" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fb4bc-68fd-7746-8673-df9bbf147bcf" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-737e-9f96-0642f7bff454" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-737e-9f96-0642f7bff454_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-737e-9f96-0642f7bff454" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-737e-9f96-0642f7bff454_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7d4e-b2fa-26b02049898e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fb4bc-68fd-737e-9f96-0642f7bff454" xlink:to="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7d4e-b2fa-26b02049898e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-70c3-9f39-9813763de104" xlink:href="drs-20260930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7d4e-b2fa-26b02049898e" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_019fb4bc-68fd-70c3-9f39-9813763de104" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-7463-80b8-619402657fbb" xlink:href="drs-20260930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fb4bc-68fd-7d4e-b2fa-26b02049898e" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_019fb4bc-68fd-7463-80b8-619402657fbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019fb4bc-68fd-7016-940e-0114370ab631" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fb4bc-68fd-7eb4-8f52-db2c66213b36" xlink:to="loc_us-gaap_Assets_019fb4bc-68fd-7016-940e-0114370ab631" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/BusinessAcquisitionsDetails" xlink:type="simple" xlink:href="drs-20260930.xsd#BusinessAcquisitionsDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/BusinessAcquisitionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019fb4bc-68fd-78c8-87eb-7f3133849851" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fb4bc-68fd-75e3-a28e-92316c258e0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fb4bc-68fd-78c8-87eb-7f3133849851" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fb4bc-68fd-75e3-a28e-92316c258e0f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019fb4bc-68fd-780f-b6fa-97b6f1dcfb6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fb4bc-68fd-75e3-a28e-92316c258e0f" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019fb4bc-68fd-780f-b6fa-97b6f1dcfb6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fb4bc-68fd-780f-b6fa-97b6f1dcfb6c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fb4bc-68fd-780f-b6fa-97b6f1dcfb6c" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fb4bc-68fd-780f-b6fa-97b6f1dcfb6c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fb4bc-68fd-763f-8643-e8646ad2f38a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fb4bc-68fd-780f-b6fa-97b6f1dcfb6c" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fb4bc-68fd-763f-8643-e8646ad2f38a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_RaftLLCMember_019fb4bc-68fd-79c4-a7cb-5e3a8c44d6ce" xlink:href="drs-20260930.xsd#drs_RaftLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fb4bc-68fd-763f-8643-e8646ad2f38a" xlink:to="loc_drs_RaftLLCMember_019fb4bc-68fd-79c4-a7cb-5e3a8c44d6ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationPriceOfAcquisitionExpected_019fb4bc-68fd-7e2d-bea3-ee5e4bbc1850" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationPriceOfAcquisitionExpected"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fb4bc-68fd-78c8-87eb-7f3133849851" xlink:to="loc_us-gaap_BusinessCombinationPriceOfAcquisitionExpected_019fb4bc-68fd-7e2d-bea3-ee5e4bbc1850" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_JasonRinskyMember_019fb4bc-6790-7282-9c78-47ffa4bb9b5d" xlink:href="drs-20260930.xsd#drs_JasonRinskyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_drs_JasonRinskyMember_019fb4bc-6790-7282-9c78-47ffa4bb9b5d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_MarkDorfmanMember_019fb4bc-6790-7b12-a3db-250b1581a57d" xlink:href="drs-20260930.xsd#drs_MarkDorfmanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_drs_MarkDorfmanMember_019fb4bc-6790-7b12-a3db-250b1581a57d" xlink:type="arc" order="3"/>
  </link:definitionLink>
</link:linkbase>
