hair·​worm ˈher-ˌwərm How to pronounce hairworm (audio)
: any of a phylum (Nematomorpha) of elongated worms that have separate sexes, are parasitic in arthropods as larvae, and are free-living in water as adults

called also horsehair worm

: any of a genus (Capillaria) of nematode worms that include serious parasites of the digestive tract of fowls and tissue and organ parasites of mammals

Examples of hairworm in a Sentence

Recent Examples on the Web Swimming with the fishesSpinochordodes tellinii, also known as a hairworm, are free-living aquatic organisms as adults, who, as nematodes, eek out an existence in the mud. Christie Wilcox, Discover Magazine, 31 Oct. 2015 Paragordius obamai, a hairworm that lives inside the stomachs of African crickets. Lisa M. Krieger, The Mercury News, 9 Jan. 2017 For his part, Obama also has a trapdoor spider, a species of lichen, a puffbird, a parasitic hairworm that infects crickets, and an extinct lizard called Obamadon named after him. Richard Pyle, National Geographic, 2 Sep. 2016

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

Word History

First Known Use

1658, in the meaning defined at sense 1

Time Traveler
The first known use of hairworm was in 1658

Dictionary Entries Near hairworm

Cite this Entry

“Hairworm.” Dictionary, Merriam-Webster, Accessed 22 Jun. 2024.

Kids Definition


hair·​worm ˈha(ə)r-ˌwərm How to pronounce hairworm (audio)
: any of various very long slender worms (as a horsehair worm)

Medical Definition


: any nematode worm of the genus Capillaria

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