WordNet (r) 3.0 (2006):

poison mercury
    n 1: climbing plant common in eastern and central United States
         with ternate leaves and greenish flowers followed by white
         berries; yields an irritating oil that causes a rash on
         contact [syn: poison ivy, markweed, poison mercury,
         poison oak, Toxicodendron radicans, Rhus radicans]