seizure has 4 distinct synonyms spread across 3 of its 4 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.
a sudden occurrence (or recurrence) of a disease
“he suffered an epileptic seizure”
the act of forcibly dispossessing an owner of property
the act of taking of a person by force
the taking possession of something by legal process
Synonyms, antonyms and the broader and narrower relations for seizure come from Princeton University’s WordNet. Full sources and licences.