act has 19 distinct synonyms spread across 10 of its 15 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 refrain.
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 suitable for theatrical performance
“This scene acts well”
be engaged in an activity, often for no particular purpose other than pleasure
a legal document codifying the result of deliberations of a committee or society or legislative body
something that people do or cause to happen
a subdivision of a play or opera or ballet
a short performance that is part of a longer program
“he did his act three times every evening”
a manifestation of insincerity
“he put on quite an act for her benefit”
Synonyms, antonyms and the broader and narrower relations for act come from Princeton University’s WordNet. Full sources and licences.