antagonist: Meaning and Definition of

an•tag•o•nist

1. a person who is opposed to, struggles against, or competes with another; opponent; adversary.
2. the adversary of the hero or protagonist of a drama or other literary work: Iago is the antagonist of Othello.
3. a muscle that acts in opposition to another. Cf. agonist (def. 3).
4. a tooth in one jaw that articulates during mastication or occlusion with a tooth in the opposing jaw.
5. a drug that counteracts the effects of another drug.