cnidaria

Cnidaria (IPA: ) is a phylum containing some 11,000 species of apparently simple animals found exclusively in aquatic, mostly marine, environments. On the other hand, their biochemistry and genetic makeup reveal that even the stationary starlet sea anemone is much more complex than it appears at the first glance.
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Noun
1. hydras; polyps; jellyfishes; sea anemones; corals
(synonym) phylum Cnidaria, Coelenterata, phylum Coelenterata
(hypernym) phylum
(member-holonym) Metazoa, subkingdom Metazoa
(member-meronym) coelenterate, cnidarian

(n. pl.)
A comprehensive group equivalent to the true Coelenterata, i. e., exclusive of the sponges. They are so named from presence of stinging cells (cnidae) in the tissues. See Coelenterata.