poison oak

American  

noun

1. either of two shrubs, Rhus toxicodendron, of the eastern United States, 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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poison oak British  

noun

1. either of two North American anacardiaceous shrubs, Rhus toxicodendron or R. diversiloba, that are related to the poison ivy and cause a similar rash See also sumach

2. (not in technical use) another name for poison ivy

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Etymology

Origin of poison oak

An Americanism dating back to 1735–45

Example Sentences

Poodle-dog isn’t a household name like poison oak and ivy, likely due to its limited geographic region and fleeting nature.

From Los Angeles Times • Apr. 5, 2025

Interesting side note: Mugwort tends to grow next to poison oak.

From Los Angeles Times • Nov. 3, 2024

He likely traipsed through poison oak while out in the wilderness and the swelling in his paws had not subsided as of Thursday, Dawes said.

From Los Angeles Times • Jul. 18, 2024

Its sparse plant life consists of scraggly shrubs and pines, along with thickets of poison oak.

From New York Times • Dec. 24, 2023

On the way, he showed me a plant called poison oak that makes you itch all over if you touch it, and told me to keep an eye out for snakes.

From "Unusual Chickens for the Exceptional Poultry Farmer" by Kelly Jones