Antagonist

ANTAG'ONIST, noun [Gr. against, and a champion. See [[Act and Agony]].]

1. One who contends with another in combat; used primarily in the Grecian games. An adversary.

2. An opponent in controversy.

3. In anatomy, a muscle which acts in opposition to another; as a flexor, which bends a part, is the antagonist of an extensor, which extends it.

ANTAG'ONIST, adjective Counteracting; opposing; combating; as, an antagonist muscle.