I. ˈagənə̇st noun
( -s )
Etymology: Late Latin agonista, from Greek agōnistēs combatant, from agōnizesthai to contend, from agōn gathering, assembly, contest — more at agony
1. : one that is engaged in a struggle: as
a. : a leading character (as the protagonist) in a literary work
the chief interest of the novel … is an analysis of the nature and moods … of the four agonists — Iris Barry
b. : one that is beset by intellectual or spiritual conflicts
an agonist , a self-tormentor who ran to meet suffering halfway — John Buchan
2.
[back-formation from antagonist “a muscle”]
: a muscle that on contracting is automatically checked and controlled by the opposing simultaneous contraction of another muscle — see antagonist 2a; compare synergist
II. noun
: a chemical substance (as a drug) capable of combining with a specific receptor on a cell and initiating the same reaction or activity typically produced by the binding of an endogenous substance — compare antagonist 2b in the Dict