What is Retaliation?

Legal Definition
The act by which a nation or individual treats another in the same manner that the latter has treated them. For example, if a nation should lay a veryheavy tariff on American goods, the United States would be justified in return in laying heavy duties on the manufactures and productions of such country. Vatt. Dr. des Gens, liv. 2, c. 18, ยง341. Vide Lex talionis.
-- Bouviers Law Dictionary
Legal Definition
The lex talionis, (q. v.)
-- Black's Law Dictionary
Legal Definition
Reprisal; retorsion.
-- Ballentine's Law Dictionary