petit mal has 2 distinct synonyms spread across 2 of its 2 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.
epilepsy characterized by paroxysmal attacks of brief clouding of consciousness (and possibly other abnormalities)
“she has been suffering from petit mal since childhood”
a seizure of short duration characterized by momentary unconsciousness and local muscle spasms or twitching
“the girl was frightened by her first petit mal”
Synonyms, antonyms and the broader and narrower relations for petit mal come from Princeton University’s WordNet. Full sources and licences.