cœlentera

from The Century Dictionary.

• A phylum or subkingdom of animals, one of the prime divisions of Metazoa, containing aquatic and almost invariably marine animals with a distinct enteric cavity opening by a mouth and communicating freely with the general body-cavity (whence the name).
• A lower series or grade of metazoic animals including the Porifera or sponges and Nematophora or cœlenterates proper: used in distinction from Cœlomata, which covers all higher Metazoa indiscriminately.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) 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.