: any of a phylum (Cnidaria) of radially symmetrical, aquatic, invertebrate animals that have a hollow digestive cavity opening to the outside by a single opening surrounded by one or more nematocyst-studded whorls of tentacles, that occur as single or colonial sessile, typically columnar polyps or usually free-swimming, bell-shaped medusae, and that include the corals, sea anemones, jellyfishes, hydras, and Portuguese man-of-wars
Welcome to the world of cnidarians—a family of sea anemones, jellyfish and other marine invertebrates that kill their enemies and prey by firing poisonous, microscopic projectiles called nematocysts. R. Weiss

called also coelenterate

cnidarian adjective

Examples of cnidarian in a Sentence

Recent Examples on the Web
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So in the new study, Tissot and her colleagues turned to the freshwater cnidarian Hydra oligactis. Bychristie Wilcox, science.org, 17 Sep. 2024 An arm and a leg Jellyfish are cnidarians, a phylum of soft-bodied invertebrates. Elizabeth Rayne, Ars Technica, 3 Jan. 2024

Word History

Etymology

New Latin Cnidaria, phylum name (from Greek knī́dē "nettle, sea nettle"—of uncertain origin— + Latin -āria, neuter plural of -ārius -ary entry 2) + -an entry 1

Note: The taxon Cnidaria is based ultimately on French cnidaire, a vernacular designation for a sub-class used by H. Milne Edwards in Histoire naturelle des coralliaires ou polypes proprements dits, tome 1 (Paris, 1857), p. 95. Milne Edwards alludes to use of Greek knī́dē for a sea nettle by Aristotle in Historia animalium, Book 5. The Greek noun has been associated with the verb knízein "to scratch, chop up, provoke" (perhaps from an Indo-European base *knid-), but the vowel length in knī́dē has no good explanation.

First Known Use

1894, in the meaning defined above

Time Traveler
The first known use of cnidarian was in 1894

Dictionary Entries Near cnidarian

Cite this Entry

“Cnidarian.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cnidarian. Accessed 14 Jan. 2025.

Kids Definition

cnidarian

noun
cnidarian adjective

Medical Definition

cnidarian

noun
cnidarian adjective

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