volatility has 3 distinct synonyms spread across 2 of its 3 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.
the property of changing readily from a solid or liquid to a vapor
the trait of being unpredictably irresolute
“the volatility of the market drove many investors away”
being easily excited
Synonyms, antonyms and the broader and narrower relations for volatility come from Princeton University’s WordNet. Full sources and licences.