meiosis has 3 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.
(genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants)
understatement for rhetorical effect (especially when expressing an affirmative by negating its contrary)
“saying `I was not a little upset' when you mean `I was very upset' is an example of litotes”
Synonyms, antonyms and the broader and narrower relations for meiosis come from Princeton University’s WordNet. Full sources and licences.