1. Poisonous shrub of the Pacific coast of North America that causes a rash on contact
   "Warning signs marked areas where western poison oak grew along the trail";
   - western poison oak, Toxicodendron diversilobum, Rhus diversiloba
    
2. Poisonous shrub of southeastern United States causing a rash on contact
   "The eastern poison oak climbed up the old oak tree";
   - eastern poison oak, Rhus quercifolia, Toxicodendron pubescens
    
3. Dermatitis resulting from contact with a poison oak plant
   "He developed a severe case of poison oak after hiking through the woods"
    
4. [non-standard] 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
   "Hikers learn to identify and avoid poison oak to prevent painful rashes";
   - poison ivy, markweed, Toxicodendron radicans, Rhus radicans

Derived forms: poison oaks

Type of: poisonous plant, Rhus dermatitis

Part of: genus Toxicodendron, Toxicodendron

Encyclopedia: Poison oak