any overt act of defiance or attack upon military (including naval) authority by two or more persons subject to such authority. The term is occasionally used to describe nonmilitary instances of defiance or attack—such as mutiny on board a merchant ship or a rising of slaves in a state in which slavery is recognized by law or custom. Mutiny should be distinguished from revolt or rebellion, which involve a more widespread defiance and which generally have a political objective.

Mutiny was regarded as a most serious offense, especially aboard ships at sea. Because the safety of the ship was thought to depend upon the submission of all persons on board to the will of the captain, wide disciplinary powers were given to the commanding officer, including the power to inflict the death penalty without a court-martial. With the development of radio communications, however, such stringent penalties have become less necessary, and, under many current military codes, sentences for mutiny can be passed only by court-martial.