The Collaborative International Dictionary of English v.0.48:

Reprisal \Re*pris"al\ (r?-priz"al), n. [F. repr?saille, It.
   ripresaglia, rappresaglia, LL. reprensaliae, fr. L.
   reprehendere, reprehensum. See Reprehend, Reprise.]
   1. The act of taking from an enemy by way of reteliation or
      indemnity.
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            Debatable ground, on which incursions and reprisals
            continued to take place.              --Macaulay.
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   2. Anything taken from an enemy in retaliation.
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   3. The act of retorting on an enemy by inflicting suffering
      or death on a prisoner taken from him, in retaliation for
      an act of inhumanity. --Vattel (Trans.)
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   4. Any act of retaliation. --Waterland.
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   Letters of marque and reprisal. See under Marque.
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WordNet (r) 3.0 (2006):

reprisal
    n 1: a retaliatory action against an enemy in wartime

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "reprisal":
   amends, avengement, avenging, blood feud, comeuppance,
   compensation, counterblow, desert, deserts, feud, getting even,
   indemnification, indemnity, just deserts, punishment, quittance,
   recompense, redress, repayment, requital, restitution, retaliation,
   retribution, revanche, revanchism, revenge, reward, sweet revenge,
   vendetta, vengeance, vindication, what is due, what is merited