flatworm

noun

flat·​worm ˈflat-ˌwərm 

: any of a phylum (Platyhelminthes) of soft-bodied usually much flattened acoelomate worms (such as the planarians, flukes, and tapeworms)

called also platyhelminth

Examples of flatworm in a Sentence

Recent Examples on the Web

The infection can come from a few sources: raw or undercooked snails or slugs, vegetables or fruit that have been contaminated by snails, slugs or flatworms or their slime, or by eating infected hosts like land crabs, freshwater prawns or frogs, doctors said. —Irene Wright, Miami Herald, 21 Feb. 2025

In this new study, Nakajima and the team focused on the group of genes that is unique to animals with high regenerative capacity like flatworms. —Laura Baisas, Popular Science, 1 Aug. 2024

Periods of heavy rain in Houston drew out a rash of invasive and toxic hammerhead flatworms. —Kelli Bender, Peoplemag, 29 July 2024

Modern-day flatworm parasites have complex life cycles involving multiple host species. —Kristi Curry Rogers, Scientific American, 1 Feb. 2024

Word History

First Known Use

1874, in the meaning defined above

Kids Definition

flatworm

noun

flat·​worm -ˌwərm 

: any of a phylum of simple worms (as planarians, flukes, or tapeworms) that have a soft flat body, lack a body cavity, and have bilateral symmetry

Medical Definition

flatworm

noun

flat·​worm ˈflat-ˌwərm 

: any worm of the phylum Platyhelminthes : platyhelminth

especially : turbellarian