poison sumac

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

• noun A shrub or small tree (Toxicodendron vernix) of eastern North American wetlands, having compound leaves and greenish-white berries and causing a rash on contact.
• noun A skin rash caused by contact with this plant.

from The Century Dictionary.

• noun A small handsome tree, Rhus venenata, of swamp-borders in eastern North America.

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

• noun A woody shrub or small tree, all parts of which cause irritation to humans; Rhus vernix or Toxicodendron vernix.

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

• noun dermatitis resulting from contact with a poison sumac plant
• noun smooth American swamp shrub with pinnate leaves and greenish flowers followed by greenish white berries; yields an irritating oil