n. Phylum Cnidaria. A group of animals that includes corals, hydras, jellyfish, Portuguese man-of-war, sea anemones, sea pens, sea whips, and sea fans; and has the defining feature of stinging structures called nematocysts. (See nematocyst.)
A phylum of animals with approximately 9000 different species. Cnidarians are radially symmetric, with tentacles originating from a central node. This phylum includes hydroids, jellyfish, anemones and corals.