Source : Webster's Revised Unabridged Dictionary (1913)

Retaliate \Re*tal"i*ate\, v. i.
   To return like for like; specifically, to return evil for
   evil; as, to retaliate upon an enemy.

Retaliate \Re*tal"i*ate\, v. t. [imp. & p. p. {Retaliated}; p.
   pr. & vb. n. {Retaliating}.] [L. retaliatus, p. p. of
   retaliare to retaliate; pref. re- re- + a word akin to talio
   talion, retaliation. Cf. {Talion}.]
   To return the like for; to repay or requite by an act of the
   same kind; to return evil for (evil). [Now seldom used except
   in a bad sense.]

         One ambassador sent word to the duke's son that his
         visit should be retaliated.              --Sir T.
                                                  Herbert.

         It is unlucky to be obliged to retaliate the injuries
         of authors, whose works are so soon forgotten that we
         are in danger of appearing the first aggressors.
                                                  --Swift.

Source : WordNet®

retaliate
     v 1: take revenge for a perceived wrong; "He wants to avenge the
          murder of his brother" [syn: {revenge}, {avenge}]
     2: make a counterattack and return like for like, especially
        evil for evil; "The Empire strikes back"; "The Giants
        struck back and won the opener"; "The Israeli army
        retaliated for the Hamas bombing" [syn: {strike back}]