Definition of Antagonist

Antagonist

1. One who contends with another, especially in combat; an adversary; an opponent.
2. A muscle which acts in opposition to another; as a flexor, which bends a part, is the antagonist of an extensor, which extends it.
3. A medicine which opposes the action of another medicine or of a poison when absorbed into the blood or tissues.
4. Antagonistic; opposing; counteracting; as, antagonist schools of philosophy.