noun
A word that has the opposite meaning of another word. Used in linguistic contexts and everyday explanations.
「大きい」の対義語は「小さい」です。
The antonym of 'big' is 'small'.
対義語を調べるときは、辞書が便利だ。
A dictionary is useful when looking up antonyms.
反対語 is a more general term for 'opposite word' and is often used interchangeably with 対義語 in everyday speech, though 対義語 is more technical.
From 対 (opposite) + 義 (meaning) + 語 (word). A straightforward compound that transparently means 'opposite-meaning word'.