Agonist

имя существительное 1) соперник, противник (в борьбе за призовое место) 2) [литературоведение] главное действующее лицо, протагонист Синоним(ы): protagonist 3) человек, раздираемый внутренними противоречиями

Большой англо-русский словарь

Agonist

noun Etymology: Late Latin agonista competitor, from Greek agōnistēs, from agōnizesthai to contend, from agōn 1. one that is engaged in a struggle 2. [from antagonist] a. a muscle that is controlled by the action of an antagonist with which it is paired b. a chemical substance capable of combining with a specific receptor on a cell and initiating the same reaction or activity typically produced by the binding endogenous substance Example: dopaminergic agonists — compare antagonist 2b

Merriam-Webster's Collegiate Dictionary