/nuy dair"ee euhn/ , n.
1. any invertebrate animal, as a hydra, jellyfish, sea anemone, or coral, considered as belonging to the phylum Cnidaria, characterized by the specialized stinging structures in the tentacles surrounding the mouth; a coelenterate.
adj.
2. belonging or pertaining to the Cnidaria.
[ CNIDARI(A) + -AN ]