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Definition of poison oak
poison oak
Plural:poison oaks
• noun
1
North American A poisonous North American shrub or vine of the cashew family that produces an irritating oil called urushiol, characterized by leaves divided into three coarsely toothed or lobed leaflets that resemble oak leaves.
Example
"While hiking through the dense California brush, they were careful to stay on the trail to avoid brushing against poison oak."
2
North American The severely itchy skin rash and allergic contact dermatitis caused by contact with the urushiol oil found on the poison oak plant.
Example
"The doctor prescribed a topical steroid cream to help alleviate the swelling and itching from her severe case of poison oak."
• Nearby Words
Usage Trend
Historical frequency of usage in published text.
180019102020
Data source: Google Books Ngram Viewer
Cite this Entry
Wordmom. (2026). Definition of Poison oak. In Wordmom Dictionary. Retrieved Oct 19, 2026, from https://wordmom.com/dictionary/poison%20oak