cow parsnip

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

• noun A tall perennial North American herb (Heracleum maximum) in the parsley family, having large compound leaves and compound umbels of small whitish flowers.

from The Century Dictionary.

• noun A wild umbelliferous plant of the genus Heracleum (which see).

from the GNU version of the Collaborative International Dictionary of English.

• (Bot.) A coarse umbelliferous weed of the genus Heracleum (Heracleum sphondylium in England, and Heracleum lanatum in America).

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

• noun Heracleum maximum, an umbelliferous herb.

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

• noun tall coarse plant having thick stems and cluster of white to purple flowers