1. Any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans
   "Swimmers were cautioned about jellyfish in the water"
    
2. Large siphonophore having a bladderlike float and stinging tentacles
   "Swimmers were warned about jellyfish in the area";
   - Portuguese man-of-war, man-of-war, man-o'-war

Derived forms: jellyfishes

Type of: cnidarian, coelenterate, siphonophore

Part of: Cnidaria, Coelenterata, genus Physalia, phylum Cnidaria, phylum Coelenterata, Physalia

Encyclopedia: Jellyfish