The Collaborative International Dictionary of English v.0.48:

Coelentera \C[oe]*len"te*ra\or Coelenterata
\C[oe]*len`te*ra"ta\, n. pl. [NL., fr. Gr. koi^los hollow + ?
   intestines.] (Zool.)
   A comprehensive group of Invertebrata, mostly marine,
   comprising the Anthozoa, Hydrozoa, and Ctenophora. The name
   implies that the stomach and body cavities are one. The group
   is sometimes enlarged so as to include the sponges.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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