agonist

US: (ag′ə nist)

WordReference Random House Unabridged Dictionary of American English © 2025

ag•o•nist  (ag′ə 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. Physiology a contracting muscle whose action is opposed by another muscle. Cf. antagonist (def. 3).
4. Drugs [Pharm.] a chemical substance capable of activating a receptor to induce a full or partial pharmacological response. Cf. antagonist (def. 5).

• Greek agōnisté̄s contestant, equivalent. to agó̄n agon + -istēs -ist
• Late Latin agōnista
• 1620–30