false has 19 distinct synonyms spread across 7 of its 11 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is true.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
in a disloyal and faithless manner
“he behaved treacherously”
3 of the 11 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for false.
Synonyms, antonyms and the broader and narrower relations for false come from Princeton University’s WordNet. Full sources and licences.