2. A marked change in appearance, character, condition, or function.
3. Biology A change in the form and often habits of an animal during normal development after the embryonic stage. Metamorphosis includes, in insects, the transformation of a maggot into an adult fly and a caterpillar into a butterfly and, in amphibians, the changing of a tadpole into a frog.
4. Pathology A usually degenerative change in the structure of a particular body tissue.
[Latin metamorphsis, from Greek, from metamorphoun, to transform : meta-, meta- + morph, form.]