Definition

Any of various free-swimming COELENTERATES having a disc- or bell-shaped body of jellylike consisten­cy. Many have long tentacles with nematocysts (stinging cells). Some are capable of producing glowing ball LUMINESCENCE. Any jellylike free-floating organism. The term 'jel­lyfish' often is applied to the ctenophores and may be applied to certain tunicates. Also called medusa.