Cnidaria

from WordNet (r) 3.0 (2006)

Cnidaria
    n 1: hydras; polyps; jellyfishes; sea anemones; corals [syn:
         {Cnidaria}, {phylum Cnidaria}, {Coelenterata}, {phylum
         Coelenterata}]

from The Collaborative International Dictionary of English v.0.48

Cnidaria \Cni*da"ri*a\ (n[i^]*d[=a]"r[i^]*[.a]), n. pl. [NL. See
   {Cnida}.] (Zool.)
   A comprehensive group equivalent to the true C[oe]lenterata,
   i. e., exclusive of the sponges. They are so named from
   presence of stinging cells (cnidae) in the tissues. See
   {Coelenterata}.
   [1913 Webster]