riot has 17 distinct synonyms spread across 5 of its 6 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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.
a public act of violence by an unruly mob
a joke that seems extremely funny
a wild gathering involving excessive drinking and promiscuity
take part in a riot; disturb the public peace by engaging in a riot
“Students were rioting everywhere in 1968”
Synonyms, antonyms and the broader and narrower relations for riot come from Princeton University’s WordNet. Full sources and licences.