Medusa
WordNet
noun
(1) One of two forms that coelenterates take: is the free-swimming sexual stage in the life cycle of a coelenterate and has a gelatinous umbrella-shaped body and tentacles
(2) Any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans
(3) (Greek mythology) a woman transformed into a Gorgon by Athena; she was slain by Perseus