overstate has 6 distinct synonyms spread across 1 of its 1 sense. 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 understate.
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.
to enlarge beyond bounds or the truth
“tended to romanticize and exaggerate this `gracious Old South' imagery”
Synonyms, antonyms and the broader and narrower relations for overstate come from Princeton University’s WordNet. Full sources and licences.