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roundworm

American

[round-wurm] / ˈraʊndˌwɜrm /

noun

any nematode, especially Ascaris lumbricoides, that infests the intestine of humans and other mammals.

roundworm British

/ ˈraʊndˌwɜːm /

noun

any nematode worm, esp Ascaris lumbricoides , a common intestinal parasite of man and pigs

"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

Etymology

Origin of roundworm

First recorded in 1555–65; round ¹ + worm

Compare meaning

How does roundworm compare to similar and commonly confused words? Explore the most common comparisons:

flatworm vs. roundworm

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Researchers from the University of Utah recently published a paper describing the tiny roundworm and formally naming it in a way that honors the Indigenous people whose ancestral lands include the lake.

From Science Daily • Jan. 10, 2026

People can become infected if they ingest soil, dirt, water or other material contaminated with raccoon feces, which could contain roundworm eggs.

From Los Angeles Times • Sep. 18, 2024

The intestinal effects of kombucha’s microbes were studied in Caenorhabditis elegans, a nematode roundworm.

From Salon • Apr. 8, 2024

The data derived from these "films" of roundworm brains were then used to create computer simulations of roundworm brains.

From Science Daily • Mar. 15, 2024

Filaria conjunctivæ, resembling Setaria equina very much in size and general appearance, is another roundworm which has been found in the eye of the horse.

From Special Report on Diseases of the Horse by Michener, Charles B.

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023