<p><strong>Noun</strong></p><ul><li>a person who is opposed to, struggles against, or competes with another</li><li>opponent</li><li>adversary</li></ul><p><strong>Synonyms</strong></p><ul><li>foe</li><li>enemy</li><li>contestant</li></ul><p><strong>Antonyms</strong></p><ul><li>friend</li><li>ally</li></ul><p><strong>Noun</strong></p><ul><li>the adversary of the hero or protagonist of a drama or other literary work</li><li>Iago is the antagonist of Othello.</li></ul><p><strong>Physiology</strong></p><ul><li>a muscle that acts in opposition to another</li></ul><p><strong>Dentistry</strong></p><ul><li>a tooth in one jaw that articulates during mastication or occlusion with a tooth in the opposing jaw</li></ul><p><strong>Pharmacology</strong></p><ul><li>a drug that counteracts the effects of another drug</li></ul><p><strong>Verb</strong></p><ul><li>to compete with in rivalry</li><li>strive to win from, equal, or outdo</li></ul><p><strong>Synonyms</strong></p><ul><li>oppose</li></ul><p><strong>Examples</strong></p><ul><li>to prove to be a worthy rival of: He soon rivaled the others in skill.</li><li>to equal (something) as if in carrying on a rivalry: The Hudson rivals any European river in beauty.</li></ul><p><strong>Synonyms</strong></p><ul><li>emulate</li><li>match</li></ul>