Definition for Cnidaria
From Biology Forums Dictionary
Cnidarians, also known as coelenterates, diverse group of aquatic, invertebrate animals armed with microscopic stinging structures. Cnidarians make up the phylum Cnidaria, which encompasses more than 9,000 species, including corals, hydras, jellyfish, Portuguese man-of-war, and sea anemones. Cnidarians live in all oceans, and a few species inhabit fresh water.