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 first is glucagon-like peptide-1 receptor agonists (or GLP-1 RAs), which mimic a naturally occurring hormone to let your brain know when your stomach is actually full. —Abhimanyu Ghoshal, New Atlas, 25 June 2025

Castration via hormone therapy can be achieved medically or surgically: Medical castration (more common) entails taking a drug, either a luteinizing hormone-releasing hormone (LHRH) agonist or an LHRH antagonist. —Matthew Wosnitzer, Verywell Health, 12 May 2025

Over the past few years, GLP-1 receptor agonist drugs have become part of many people’s treatment regimens. —Dr. Jamin Brahmbhatt, CNN Money, 14 July 2025

Patients treated with semaglutide had a 46 percent lower risk of developing ADRD than those receiving insulin, a 33 percent lower risk than those on metformin, and a 20 percent lower risk than those on earlier GLP-1 agonists. —Jenna Sundel, MSNBC Newsweek, 25 June 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