1. (n.) One who contends with another, especially in combat; an adversary; an opponent.

2. (n.) 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. (n.) A medicine which opposes the action of another medicine or of a poison when absorbed into the blood or tissues.

4. (a.) Antagonistic; opposing; counteracting; as, antagonist schools of philosophy.

Roscius actor actress adversary anti antihero archenemy assailant bad guy barnstormer bit bit part bitter enemy cast character character actor character man character woman child actor combatant competition competitor con contender cue devil diseur diseuse dramatizer enemy fat part feeder foe foeman foil heavy hero heroine histrio histrion ingenue juvenile lead lead role leading lady leading man leading woman lines match matinee idol mime mimer mimic monologist mummer open enemy opponent opposer opposing party opposite camp opposition oppugnant pantomime pantomimist part person personage piece playactor player protagonist protean actor public enemy reciter role side soubrette stage performer stage player stooge straight man straight part stroller strolling player supporting character supporting role sworn enemy the loyal opposition the opposition theatrical thespian title role trouper utility man villain walk-on walking part