(A) To take action against another in a vengeful fashion as a result of some prior act. For example, as a result of a tenant not paying rent on time, an angry landlord may shut off the heat to the tenant’s apartment. (B)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 very heavy tariff on American goods, the United States would be justified in return in laying heavy duties on the manufactures and productions of such country.