flatworm

American

[flat-wurm] / ˈflætˌwɜrm /

noun

any worm of the phylum Platyhelminthes, having bilateral symmetry and a soft, solid, usually flattened body, including the planarians, tapeworms, and trematodes; platyhelminth.

flatworm British

/ ˈflætˌwɜːm /

noun

any parasitic or free-living invertebrate of the phylum Platyhelminthes , including planarians, flukes, and tapeworms, having a flattened body with no circulatory system and only one opening to the intestine

"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

flatworm Scientific

/ flăt′wûrm′ /

Any of various parasitic and nonparasitic worms of the phylum Platyhelminthes, characteristically having a soft, flat, bilaterally symmetrical body. Flatworms lack a coelom (body cavity), respiratory system, and circulatory system, but are the most primitive invertebrates to have a brain. The evolutionary history of flatworms is uncertain, but they share some basic characteristics with rotifers, nematodes, and a few other invertebrate phyla. Cestodes (tapeworms), planarians, and trematodes (flukes) are flatworms.

Etymology

Origin of flatworm

First recorded in 1895–1900; flat ¹ + worm

Compare meaning

How does flatworm 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.

See Examples For:

flatworm

Previous research into flatworm regeneration has shown that the hormone activin plays an important role in their survival.

From Science Daily ● Aug. 5, 2026

A parasite called Heterobilharzia americana, a flatworm commonly referred to as liver fluke, was behind the illness of the 11 dogs.

From Los Angeles Times ● Mar. 14, 2024

That's the reality for ants infected with the lancet liver fluke, a tiny parasitic flatworm.

From Science Daily ● Sep. 17, 2023

California killifish infected with a trematode flatworm, for example, are 10 times to 30 times more likely to become meals for birds than uninfected fish.

From New York Times ● Jan. 9, 2023

If a flatworm be cut in two, the front piece grows out a new tail, the hind piece a new head, and two perfect worms result.

From Biology A lecture delivered at Columbia University in the series on Science, Philosophy and Art November 20, 1907 by Edmund Beecher Wilson

Random Word

Spin the wheel and learn a new word!

Get a word

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