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

At this year's ADA, Lilly also presented Phase 3 results from its triple agonist retatrutide. —Angelica Peebles, CNBC, 13 June 2026

Unlike semaglutide, the active ingredient in Ozempic and Wegovy, BRP is not a GLP-1 agonist. —Allison Palmer updated June 13, Miami Herald, 13 June 2026

These drugs, including glucagon-like peptide-1 (GLP-1) receptor agonists, work by targeting the circuitry that drives satiety. —Isabella Backman, Hartford Courant, 12 June 2026

One patient who has obesity, PCOS and who lost dozens of pounds on a dual GIP/GLP-1 agonist cannot even get coverage of older anti-obesity medications because her BMI is now normal. —Karen R. Studer, Sacbee.com, 1 June 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