/ag"euh nist/ , n.
1. a person engaged in a contest, conflict, struggle, etc., esp. the protagonist in a literary work.
2. a person who is torn by inner conflict.
3. Physiol. a contracting muscle whose action is opposed by another muscle. Cf. antagonist (def. 3).
4. Pharm. a chemical substance capable of activating a receptor to induce a full or partial pharmacological response. Cf. antagonist (def. 5).
[ 1620-30; agonista agonistés contestant, equiv. to agón AGON + -istes -IST ]