nem·​a·​to·​cyst ˈne-mə-tə-ˌsist How to pronounce nematocyst (audio)
: 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 Jellyfish tentacles have thousands of nematocysts that can pierce the skin and inject venom. Nick Blackmer, Verywell Health, 29 June 2023 The mostly transparent jellyfish typically have a reddish-orange or yellow cross in the center of their bodies, as well as 60 to 80 short and long tentacles with nematocysts or stinging cells, the department said. Saleen Martin, USA TODAY, 8 June 2023 Its tentacles contain stinging nematocysts that can deliver venom capable of paralyzing and killing small fish and crustaceans. Leada Gore |, al, 15 Mar. 2023 But the authors point out that these nematocysts can only be fired once, like a harpoon, remaining in the target. Jennifer Ouellette, Ars Technica, 7 Mar. 2023 In each is a structure called a nematocyst which contains the venom and a harpoon-like structure on a biological thread. Christie Wilcox, Discover Magazine, 2 June 2015 When the nematocyst fires, the shaft is ejected first and turns right-side out. Viviane Callier, Scientific American, 18 Aug. 2022 Now a team led by Matt Gibson and Ahmet Karabulut of the Stowers Institute for Medical Research in Kansas City, Mo., has used cutting-edge imaging technology to study nematocyst firing in very fine detail. Viviane Callier, Scientific American, 18 Aug. 2022 Using super-resolution fluorescence and electron microscopes, the researchers observed a detailed sequence of events involving a stiff shaft and a flexible, whiplike filament that starts out coiled around it within the nematocyst. Viviane Callier, Scientific American, 18 Aug. 2022

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'nematocyst.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


International Scientific Vocabulary

First Known Use

1862, in the meaning defined above

Time Traveler
The first known use of nematocyst was in 1862

Dictionary Entries Near nematocyst

Cite this Entry

“Nematocyst.” Dictionary, Merriam-Webster, Accessed 19 Jul. 2024.

Kids Definition


nem·​a·​to·​cyst ˈnem-ət-ə-ˌsist How to pronounce nematocyst (audio)
: one of the tiny stinging organs of various coelenterates (as jellyfishes and corals) used in catching prey

Medical Definition


nem·​a·​to·​cyst ˈnem-ət-ə-ˌsist How to pronounce nematocyst (audio) ni-ˈmat-ə- How to pronounce nematocyst (audio)
: one of the minute stinging organelles of various coelenterates

called also stinging cell

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