The term 'military adversary' can be defined as an ENEMY, which is a five-letter word. A military adversary is an opposing force in a conflict, usually a nation or group of nations, that is hostile to another nation or group of nations. It is typically used to describe a situation in which two or more countries are engaged in a war or other type of armed conflict. In some cases, a military adversary may also refer to a non-state actor, such as a terrorist organization, that is hostile to a nation or group of nations.