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.

To better understand the broader impact of the discovery, the researchers studied the effects of leucine metabolism in the tiny roundworm Caenorhabditis elegans.

From Science Daily • May 21, 2026

Ascaris lumbricoides, a type of roundworm from pigs that has been reported in a few cases in humans, can cause issues with the lungs or growth problems in children in severe cases.

From Salon • May 18, 2025

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 roundworm Caenorhabditis elegans is a favorite among neuroscientists because its 302 neurons are completely mapped.

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