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

Its structure puts it into a completely separate class of synthetic opioid agonists, though, one that preclinical studies suggest may affect breathing and blood flow at far lower doses than even fentanyl. — New Atlas, 30 Sep. 2026

Existing glucagonlike peptide 1 (GLP-1) receptor agonist drugs such as semaglutide, sold as Ozempic and Wegovy, bind to GLP-1 hormone receptors in the brain, where the receptors help regulate hunger. — Jackie Flynn Mogensen, Scientific American, 29 Sep. 2026

The Danish drugmaker has licensed from Hengrui Pharma a once-weekly, oral GLP-1/GIP receptor agonist that is ready for Phase 1 clinical development. — Meghana Keshavan, STAT, 29 Sep. 2026

That includes retatrutide, a triple-agonist that targets three gut hormones and has produced greater weight loss than existing obesity drugs in clinical trials. — Annika Kim Constantino,elsa Ohlen, CNBC, 25 Sep. 2026

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