stinging nettle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A perennial nettle (Urtica dioica) native to Eurasia and widely distributed in North America. It is sometimes used medicinally, and the young leaves are edible.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A nettle; any of the species of genus Urtica that cause painful short-term skin irritation, especially Urtica dioica, originally Eurasian, now naturalized elsewhere.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun perennial Eurasian nettle established in North America having broad coarsely toothed leaves with copious stinging hairs