Entry 1 sense Webster, 1913 Antonym /ǎnt′ənĭm'/ · An·to·nym · IPA /ˈæn.təˌnɪm/ 01 n. A word of opposite meaning; a counterterm; -- used as a correlative of synonym. 1. A word of opposite meaning; a counterterm; -- used as a correlative of synonym.[R.]