An example of to retaliate is for a person to punch someone who has hit him.
Origin of retaliate; from Late Latin retaliatus, past participle of retaliare, to require, retaliate ; from Classical Latin re-, back + talio, punishment in kind (see talion), akin to Welsh t?l, compensation
verbre·tal·i·at·ed, re·tal·i·at·ing, re·tal·i·ates
Origin of retaliateLate Latin retāliāre, retāliāt- : Latin re-, re- + Latin tāliō, punishment in kind; see tel&schwa;- in Indo-European roots.
- re·tal′i·a′tive, re·tal′i·a·to′ry
(third-person singular simple present retaliates, present participle retaliating, simple past and past participle retaliated)