western poison oak wes·tern·poi·sonoak uncommon noun 1. poisonous shrub of the Pacific coast of North America that causes a rash on contact Synonymswestern poison oakToxicodendron diversilobumRhus diversiloba Related words Broader terms poisonous plant Parts Toxicodendron WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
