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

The weight-loss products are called GLP-1 agonists. —NPR, 21 Nov. 2025

Semaglutide and tirzepatide, the active ingredient in Mounjaro, are GLP-1 agonists that were first developed to treat diabetes and have also been approved in many countries for the treatment of obesity. —Mithil Aggarwal, NBC news, 8 Nov. 2025

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

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

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