Law a retaliation; reprisal; esp., in international law, mistreatment by one country of the citizens or subjects of another in retaliation for similar mistreatment received
See retorsion in American Heritage Dictionary 4
or re·tor·tion(rĭ-tôrˈshən)
noun
An act perpetrated by one nation upon another in retaliation or reprisal for a similar act perpetrated by the other nation.