› armed fighting between two or more countries or groups, or a particular example of such fighting: [C] Can any country fight two wars at the same time? [U] War is something to avoid. [U] Several nations were at war. › A war can also be any situation in which there is strong competition between opposing sides or a joint effort against something harmful: [C] Airlines engage in fare wars to attract new customers. [U] It sometimes seems like the war on cancer has stalled.