antagonist

[an-tag-uh-nist] /ænˈtæg ə nɪst/

noun

a person who is opposed to, struggles against, or competes with another; opponent; adversary.

the adversary of the hero or protagonist of a drama or other literary work:

Iago is the antagonist of Othello.

Physiology. a muscle that acts in opposition to another.

Compare agonist (def 3).

Dentistry. a tooth in one jaw that articulates during mastication or occlusion with a tooth in the opposing jaw.

Pharmacology. a drug that counteracts the effects of another drug.

Origin

1590-1600; < Late Latin antagōnista < Greek antagōnistḗs. See antagonize, -ist

Can be confused

antagonist, proponent, protagonist.

Synonyms

1. contestant, enemy, foe. See adversary.

Antonyms

1. ally, friend.

Examples from the web for antagonist

With no strong antagonist, the plot is a bit tepid (although always plausible).
Caffeine is an antagonist for the neurotransmitter adenosine.
It's not love that Conroy feels for his old antagonist but a sense of triumph.
Development just like its antagonist, corruption, occurs in degrees.
He seems to specialize in playing the audience's antagonist.
As it turned out — and always does in the movies — the antagonist miscalculated.
But Sammy dodged easily and came at his antagonist from a different angle.
She gradually reads her own resilience in the eyes of her antagonist.
Nature, and the need to regard it as an ally rather than an antagonist, was one of his constant preoccupations.
Then of course, a drug can act as an antagonist, which means that it binds to the receptor and inhibits that receptors activity.

British Dictionary definitions for antagonist

antagonist

/ænˈtæɡənɪst/

noun

an opponent or adversary, as in a contest, drama, sporting event, etc

any muscle that opposes the action of another Compare agonist (sense 1)

a drug that counteracts the effects of another drug Compare synergist (sense 1)

Word Origin and History for antagonist

1590s, from French antagoniste (16c.) or directly from Late Latin antagonista, from Greek antagonistes "competitor, opponent, rival," agent noun from antagonizesthai "to struggle against, oppose, be a rival," from anti- "against" (see anti-) + agonizesthai "to contend for a prize," from agon "contest" (see agony). Originally in battle or sport, extended 1620s to any sphere of human activity.

antagonist in Medicine

antagonist an·tag·o·nist (ān-tāg'ə-nĭst)
n.
Something, such as a muscle, disease, or physiological process, that neutralizes or impedes the action or effect of another.

antagonist in Science

antagonist

(ān-tāg'ə-nĭst)

A muscle that opposes the action of another muscle, as by relaxing while the other one contracts, thereby producing smooth, coordinated movement.
A chemical substance, such as a drug, that interferes with the physiological action of another substance, especially by combining with and blocking its nerve receptor. Compare agonist.