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 a pilot study published in Scientific Reports, researchers found that GLP-1 agonists (which mimic the effects of GLP-1 compounds) slowed the speed at which alcohol enters the bloodstream, which also slowed effects on the brain. —Scott Lafee, San Diego Union-Tribune, 25 Nov. 2025

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

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