Dictionary
pla•nar•i•an
Pronunciation: (plu-nâr'ē-un), [key]—
n. Zool.
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.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.