metamorphosis has 2 distinct synonyms spread across 2 of its 3 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.
the marked and rapid transformation of a larva into an adult that occurs in some animals
a striking change in appearance or character or circumstances
“the metamorphosis of the old house into something new and exciting”
Synonyms, antonyms and the broader and narrower relations for metamorphosis come from Princeton University’s WordNet. Full sources and licences.
a complete change of physical form or substance especially as by magic or witchcraft