agonist

noun

ag·​o·​nist ˈa-gə-nist 

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

dopaminergic agonists

compare antagonist sense 2b

Examples of agonist in a Sentence

Recent Examples on the Web

In RenBio’s case, the researchers spelled out the instructions to make a GLP-1 receptor agonist protein — essentially the same active ingredient in medicines like Ozempic and Mounjaro — and looped it into a small circle called a plasmid. —Brenda Goodman, CNN Money, 4 Nov. 2025

An earlier version of this story mistakenly said that GLP-1 agonist drugs were first approved to treat obesity in 2021. —Yuki Noguchi, NPR, 28 Oct. 2025

Researchers at Virginia Tech's Fralin Biomedical Research Institute analyzed how 20 adults with obesity — half of whom had been taking GLP-1 receptor agonists for at least four weeks — reacted to alcoholic drinks compared to participants not on the drugs. —Deirdre Bardolf, FOXNews.com, 26 Oct. 2025

The medications — taken weekly by injection in the thigh, stomach or arm — are brand names for semaglutide, which works in the brain like a GLP-1 agonist to impact satiety. —Cara Lynn Shultz, PEOPLE, 21 Oct. 2025

Word History

Etymology

borrowed from Late Latin agōnista, borrowed from Greek agōnistḗs, from agōnízesthai "to contend, fight" + -istēs -ist entry 1 — more at agonize

First Known Use

1658, in the meaning defined at sense 1

Rhymes for agonist

• antagonist
• protagonist

Medical Definition

agonist

noun

ag·​o·​nist ˈag-ə-nəst 

1

: a muscle that on contracting is automatically checked and controlled by the opposing simultaneous contraction of another muscle

called also agonist muscle, prime mover

compare antagonist sense a, synergist sense 2

2

: a chemical substance (as a drug) capable of combining with a receptor on a cell and initiating the same reaction or activity typically produced by the binding of an endogenous substance

binding of adrenergic agonists

compare antagonist sense b