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

See Examples For:

poison oak

Once you’re above the residential lots, you’ll see pipes along the way, carrying water down the hill, along with occasional trailside poison oak.

From Los Angeles Times ● Jan. 5, 2026

Plenty of cow patties, though, and a few patches of poison oak, which turns up often near Big Sur trails.

From Los Angeles Times ● Oct. 29, 2025

Rangers describe the trail — a steep half-mile to reach the cave, then a half-mile loop inside — as “strenuous,” featuring possible encounters with poison oak, bees, rattlesnakes and falling rocks.

From Los Angeles Times ● Apr. 7, 2025

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

From New York Times ● Dec. 24, 2023

He talks about the plans for the house: the skylights, expanding the deck, planting flower beds of tulips and crocuses, clearing the poison oak, adding another wing, building a Japanese-style tile bathroom.

From "The Joy Luck Club" by Amy Tan