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[nahy-dair-ee-uh n]
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  1. any invertebrate animal, as a hydra, jellyfish, sea anemone, or coral, considered as belonging to the phylum Cnidaria, characterized by the specialized stinging structures in the tentacles surrounding the mouth; a coelenterate.
  1. belonging or pertaining to the Cnidaria.

Origin of cnidarian

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for cnidarian


  1. any invertebrate of the phylum Cnidaria, which comprises the coelenterates
  1. of, relating to, or belonging to the Cnidaria

Word Origin

C20: from New Latin Cnidaria, from Greek knidē nettle
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

cnidarian in Science


  1. Any of various invertebrate animals of the phylum Cnidaria, having a body with radial symmetry and tentacles that bear microscopic stinging capsules called nematocysts. The tentacles surround a mouth that opens into a saclike internal cavity and that is used both for ingesting food and for eliminating wastes. Cnidarians evolved in the Precambrian Era, but it is not known from what type of organism. Cnidarians include the jellyfishes, hydras, sea anemones, and corals.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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