definition of
agonist

[1] #1 agonist n. [protagonist] the principal character in a work of fiction. wn

[2] #2 agonist n. someone involved in a contest or battle (as in an agon). wn

[3] #3 agonist n. a muscle that contracts while another relaxes; "when bending the elbow the biceps are the agonist". wn

[4] #4 agonist n. (biochemistry) a drug that can combine with a receptor on a cell to produce a physiological reaction. wn