steam has 2 distinct synonyms spread across 2 of its 7 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.
emit steam
“The rain forest was literally steaming”
get very angry
“her indifference to his amorous advances really steamed the young man”
cook something by letting steam pass over it
“just steam the vegetables”
water at boiling temperature diffused in the atmosphere
Synonyms, antonyms and the broader and narrower relations for steam come from Princeton University’s WordNet. Full sources and licences.