say it: an-TAG-uh-nuhst
antagonist is a noun meaning "someone who offers opposition". It carries 3 recorded senses.
a muscle that relaxes while another contracts
“when bending the elbow the triceps are the antagonist”
a drug that neutralizes or counteracts the effects of another drug
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for antagonist come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.