(n.) A word of opposite meaning\; a counterterm; -- used as a correlative of synonym.

antipode antipodes antipole antithesis articulation contra converse counter counterbalance countercheck counterpoint counterpoise counterpole counterterm expression foil free form homograph homonym homophone inverse lexeme linguistic form locution logos metonym minimum free form monosyllable obverse offset opposite opposite number polysyllable reverse setoff syllable synonym term the contrary the other side usage utterance verbalism verbum vis-a-vis vocable word