Poison oak Meaning, Definition & Usage

  1. noun dermatitis resulting from contact with a poison oak plant
  2. noun 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
    poison mercury; poison ivy; Toxicodendron radicans; markweed; Rhus radicans.

WordNet

Definitions
  1. (Bot.), the poison ivy; also, the more shrubby Rhus diversiloba of California and Oregon.

Webster 1913