noun (plural medusae /-sē, -sī, -zē, -zī/ or medusas)Zoology
- a free-swimming sexual form of a coelenterate such as a jellyfish, typically having an umbrella-shaped body with stinging tentacles around the edge. In some species, medusae are a phase in the life cycle that alternates with a polypoid phase. Compare with polyp.
mid 18th century: named by association with Medusa