[ pluh-nair-ee-uh n ]
/ pləˈnɛər i ən /

noun Zoology.

any of various free-swimming, mostly freshwater flatworms of the class Turbellaria, having an undulating or sluglike motion: popular in laboratory studies for the ability to regenerate lost parts.

Origin of planarian

1885–60; < New Latin Planari(a) a flatworm genus (noun use of feminine of Late Latin plānārius level, on level ground; taken to mean “flat”; see plane1, -ary + -an Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Examples from the Web for planarian

British Dictionary definitions for planarian

/ (pləˈnɛərɪən) /


any free-living turbellarian flatworm of the mostly aquatic suborder Tricladida, having a three-branched intestine

Word Origin for planarian

C19: from New Latin Plānāria type genus, from Late Latin plānārius level, flat; see plane 1
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

Scientific definitions for planarian

[ plə-nârē-ən ]

Any of various small, chiefly freshwater flatworms of the class Turbellaria, having soft, broad, ciliated bodies shaped like a leaf. Planarians have a mouth on their lower side that is often closer to the tail than the head, and a three-branched digestive cavity. If a planarian is cut into several pieces, each piece can grow into a whole new organism.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.