Synonyms for Jellyfish (same or very similar meaning)
WordNet sense 1 (large siphonophore having a bladderlike float and stinging tentacles):
man-of-war, Portuguese man-of-warWordNet sense 2 (any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans):
medusa, medusanFrom the ODE community, based on WordNetadd/edit