fit has 27 distinct synonyms spread across 10 of its 16 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 unfit.
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.
be the right size or shape; fit correctly or as desired
“This piece won't fit into the puzzle”
insert or adjust several objects or people
“Can you fit the toy into the box?”
conform to some shape or size
“How does this shirt fit?”
meeting adequate standards for a purpose
“a fit subject for discussion”
physically and mentally sound or healthy
“felt relaxed and fit after their holiday”
Synonyms, antonyms and the broader and narrower relations for fit come from Princeton University’s WordNet. Full sources and licences.
a sudden flurry of activity (often for no obvious reason)
“a burst of applause”