: triclad
especially : any of various dark-colored freshwater triclad flatworms (family Planariidae) with two eyespots and a triangular head

Examples of planarian in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
This capacity is all too evidently lacking in humans—so how do planarians do it? Philip Ball, Scientific American, 18 Apr. 2023 Even a small part of a planarian can regenerate into a full worm with the typical shape and proportions. Philip Ball, Scientific American, 18 Apr. 2023

Word History

Etymology

New Latin Planaria

First Known Use

1854, in the meaning defined above

Time Traveler
The first known use of planarian was in 1854

Browse Nearby Words

Cite this Entry

“Planarian.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/planarian. Accessed 9 Mar. 2025.

Kids Definition

planarian

noun
: any of an order of small soft-bodied mostly water-dwelling flatworms having cilia
especially : one living in fresh water and having two eyespots and a triangular head

Medical Definition

planarian

noun
: any of the family Planariidae or order Tricladida comprising small soft-bodied ciliated mostly aquatic turbellarian worms
planarian adjective

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