Dictionary.com

poison oak

noun

either of two shrubs, Rhus toxicodendron, of the eastern U.S., or R. diversiloba, of the Pacific coast of North America, resembling poison ivy and causing severe dermatitis when touched by persons sensitive to them.

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Also called poison ivy.

Origin of poison oak

An Americanism dating back to 1735–45

Words nearby poison oak

poison gas, poison haw, poison hemlock, poisoning, poison ivy, poison oak, poisonous, poison-pen, poison-pen letter, poison pill, poison sumac
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for poison oak

British Dictionary definitions for poison oak

poison oak

noun

either of two North American anacardiaceous shrubs, Rhus toxicodendron or R. diversiloba, that are related to the poison ivy and cause a similar rashSee also sumach (def. 1)
(not in technical use) another name for poison ivy
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for poison oak

poison oak

n.

Either of two shrubs, Rhus toxicodendron of the southeast United States or R. diversiloba of western North America, related to poison ivy and causing a rash on contact.
poison ivy
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.