1.Definition: (biochemistry) a drug that can combine with a receptor on a cell to produce a physiological reaction

Category: Objects

2.Definition: a muscle that contracts while another relaxes

"When bending the elbow the biceps are the agonist"

Category: General

3.Definition: someone involved in a contest or battle (as in an agon)

Category: People

4.Definition: the principal character in a work of fiction

Related Noun(s):protagonist

Category: People