Jellyfish

A soft-bodied sea animal with a bell-shaped top and trailing tentacles. Many jellyfish can sting, and they drift through the ocean, often moved by currents.

A compound of “jelly,” for the soft, wobbly texture, and “fish,” a common old label for many sea creatures, even if they weren’t true fish. The term appears in English from the 18th century. Biologically, jellyfish are not fish but cnidarians, related to corals and sea anemones.