*markweed*

n. A climbing plant (Toxicodendron radicans) common in eastern and central U. S. with ternate leaves and greenish flowers followed by white berries. It yields an irritating oil that causes a rash on contact; commonly called poison ivy.
Syn. -- poison ivy, poison mercury, poison oak, Toxicodendron radicans, Rhus radicans. [ WordNet 1.5 ]