[pro.tag.o.nist] n [Gk protagonistes, fr. prot- prot- + agonistes competitor at games, actor, fr. agonizesthai to compete, fr. agon contest, competition at games--more at agony] (1671) 1 a: the principal character in a literary work (as a drama or story) b: a leading actor, character, or participant in a literary work or real event
2: a leader, proponent, or supporter of a cause: champion
3: a muscle that by its contraction actually causes a particular movement