A: Agonist: Wiktionary: Wandering Wikis
Channel: Wandering Wikis [See: Moribund Inst.]
Date: 2021-04-27

1. Someone involved in a contest or battle (as in an agon), protagonist.
2. The muscle that contracts while the other relaxes.
When bending the elbow, the biceps is the agonist.
3. (biochemistry, pharmacology) A molecule that can combine with a receptor on a cell to produce a physiological reaction.
Acetylcholine is an agonist at the cholinergic receptor.

Wiktionary contributors, "agonist," Wiktionary, The Free Dictionary, https://en.wiktionary.org/w/index.php?title=agonist&oldid=60255144 (accessed April 27, 2021).