Changing into a different form or appearance especially a fantastic or grotesque one

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Transmogrification \Trans*mog`ri*fi*ca"tion\, n. The act of transmogrifying, or the state of being transmogrified; transformation. [Colloq.] Clive, who wrote me about the transmogrification of our schoolfellow, an attorney's son. --Thackeray.

WordNet Word definitions in WordNet
n. the act of changing into a different form or appearance (especially a fantastic or grotesque one); "the transmogrification of the prince into a porcupine"

Wiktionary Word definitions in Wiktionary
n. the act or process of being transformed into a different form