medusa (n.)

"jellyfish," 1758, as genus name, from Medusa, the name of one of the three Gorgons with snakes for hair, whose glance turned to stone whomever looked upon it (attested in English from late 14c.). Her name is from Greek Medousa, literally "guardian," fem. present participle of the verb medein "to protect, rule over" (from PIE root *med- "take appropriate measures"). The zoological name was chosen by Linnæus, suggested by the creature's long tentacles. Related: Medusoid.

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Definitions of medusa from WordNet
medusa (n.)
one of two forms that coelenterates take: it is the free-swimming sexual phase in the life cycle of a coelenterate; in this phase it has a gelatinous umbrella-shaped body and tentacles;
Synonyms: medusoid / medusan
Medusa (n.)
(Greek mythology) a woman transformed into a Gorgon by Athena; she was slain by Perseus;