medusa
n. countablen. a type of jellyfish that has a body shaped like a bell or an umbrella. It usually has long tentacles that hang down and can sting.
n. the free-swimming, sexually reproducing life stage of a cnidarian, typically characterized by a gelatinous bell-shaped body and trailing tentacles. Often contrasted with the sessile polyp stage.
The medusa floated gracefully through the clear blue water.
During the summer months, the bay is filled with the medusa stage of several local jellyfish species.
In many hydrozoan life cycles, the medusa is the mobile phase responsible for the dispersal of gametes across vast oceanic distances.
From Middle English Medusa, Meduse, from Latin Medūsa, from Ancient Greek Μέδουσα (Médousa), from μέδω (médō, “rule over”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
When capitalized, refers to the figure from Greek mythology with snakes for hair; in zoology, it is a common noun for the jellyfish form.
Last updated May 8, 2026