/an tag"euh nist/ , n.
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. Physiol. a muscle that acts in opposition to another. Cf. agonist (def. 3).
4. Dentistry. a tooth in one jaw that articulates during mastication or occlusion with a tooth in the opposing jaw.
5. Pharm. a drug that counteracts the effects of another drug.
[ 1590-1600; antagonista antagonistés. See ANTAGONIZE, -IST ]
Syn. 1. contestant, enemy, foe. See adversary .
Ant. 1. ally, friend.