The marked and rapid transformation of a larva into an adult that occurs in some animals WordNet 3.0 & Open English WordNet

Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Wikipedia

Biological process by which an animal physically develops after birth. Wikipedia Disambiguation

Profound change in body structure during the postembryonic development of an organism Wikidata

A change from one form to another. OmegaWiki

A change in the form and often habits of an animal after the embryonic stage during normal development. (e.g. the transformation of a caterpillar into a butterfly or a tadpole into a frog.). Wiktionary

In biology. Wiktionary (translation)