steal has 5 distinct synonyms spread across 3 of its 5 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.
an advantageous purchase
“she got a bargain at the auction”
a stolen base; an instance in which a base runner advances safely during the delivery of a pitch (without the help of a hit or walk or passed ball or wild pitch)
Synonyms, antonyms and the broader and narrower relations for steal come from Princeton University’s WordNet. Full sources and licences.