nem·​a·​to·​cyst | \ ˈne-mə-tə-ˌsist How to pronounce nematocyst (audio) , ni-ˈma-tə- \

Definition of nematocyst

: one of the stinging capsular organelles of the tentacle of a cnidarian (such as a box jellyfish or sea anemone) that contains a coiled, hollow, usually barbed, venomous thread which is discharged especially for catching prey and defending against enemies Each nematocyst contains a spiral-coiled thread tipped with a toxin-bearing barb that can be ejected into the skin.— Peter F. Weller

called also cnidocyst

Examples of nematocyst in a Sentence

Recent Examples on the Web The tentacles contain stinging nematocysts that can deliver venom capable of paralyzing and killing small fish and crustaceans and cause extreme pain and welts to humans. Leada Gore,, 1 Mar. 2018 The blue dragon steals stinging cells, called nematocysts, from man-of-wars, storing them in specialized organs in the tips of their cerata, or wings—which may explain their name. Liz Langley, National Geographic, 28 Jan. 2017 Researchers initially thought these nematocysts might be genetically similar to those of cnidarians, animals such as jellyfish and sea anemones. Rachel Brown, National Geographic, 5 Apr. 2017 Polykrikos cells have a capsule, called a nematocyst, that contracts to propel a sharp stylet through the water—and through the armor of another microbe. Rachel Brown, National Geographic, 5 Apr. 2017 Some have sharp skeletons and tentacles with nematocysts (stinging cells) that immobilize prey. Bonnie Berkowitz,, 30 June 2017 A jellyfish’s tentacles do seem to be an odd choice of meal: humans are wary of their sting, which occurs when skin contact triggers small, harpoon-like structures called nematocysts to inject venoms that attack the victim’s cells. Rachel Brown, National Geographic, 27 June 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'nematocyst.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of nematocyst

1862, in the meaning defined above

History and Etymology for nematocyst

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The first known use of nematocyst was in 1862

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Cite this Entry

“Nematocyst.” Dictionary, Merriam-Webster, Accessed 19 Jan. 2022.

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More Definitions for nematocyst


nem·​a·​to·​cyst | \ ˈnem-ət-ə-ˌsist How to pronounce nematocyst (audio) , ni-ˈmat-ə- How to pronounce nematocyst (audio) \

Medical Definition of nematocyst

: one of the minute stinging organelles of various coelenterates

called also stinging cell

More from Merriam-Webster on nematocyst Encyclopedia article about nematocyst


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