The hemp nettle plant.
hemp nettle definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
any of a genus (Galeopsis) of European plants of the mint family; esp., a common prickly weed (G. tetrahit) now found in the U.S.
hemp nettle definition by American Heritage Dictionary
Any of various Eurasian plants of the genus Galeopsis, having bristly stems and white or reddish flowers with two lips.