Dictionary.net

large siphonophore having a bladderlike float and stinging tentacles

any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans

large siphonophore having a bladderlike float and stinging tentacles

any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans

Free swimming marine cnidarians. Most of the large jellyfish are in the class Scyphozoa; the small jellyfish are in the class Hydrozoa (HYDRA).