any invertebrate of the phylum Cnidaria, which comprises the coelenterates
adjective
2.
of, relating to, or belonging to the Cnidaria
Word origin
C20: from New Latin Cnidaria, from Greek knidē nettle
cnidarian in American English
(nɪˈdɛriən)
noun
any of a phylum (Cnidaria) of invertebrate animals, mainly marine, including jellyfishes, hydrozoans, and anthozoans, characterized by stinging cells and a saclike body cavity with a single opening for ingesting food and eliminating wastes; coelenterate
Word origin
ModL Cnidaria < Gr knidē, nettle + -aria: so called for the creatures' stinging cells