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

How GLP-1s work GLP-1 receptor agonists work by mimicking a hormone called glucagon-like peptide-1, which is released from the gut after eating. —Melissa Rudy, FOXNews.com, 10 Sep. 2025

The study found that most women in Australia prescribed GLP-1 receptor agonists—medications originally developed for type 2 diabetes, but now widely used for weight loss—were not using effective contraception, despite potential risks to pregnancy and unborn babies. —Daniella Gray, MSNBC Newsweek, 9 Sep. 2025

Wegovy, Zepbound, and other GLP-1 agonists have given Americans an extraordinary new tool for losing weight and improving their health. —Sally Pipes, Forbes.com, 2 Sep. 2025

Centrally acting alpha agonists help prevent the nervous system from responding to stress. —Jen Christensen, CNN Money, 30 Aug. 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