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