poison oak

noun

1

: any of several plants related to poison ivy and producing an oil with similar irritating properties: such as

a

: a bushy plant (Toxicodendron diversilobum synonym Rhus diversiloba) of the Pacific coast

b

: a bushy plant (Toxicodendron pubescens synonym Rhus toxicodendron) chiefly of the southeastern U.S.

2

: poison ivy sense 1a

Examples of poison oak in a Sentence

Recent Examples on the Web

Poison sumac, for instance, is a member of the Anacardiaceae family, which includes poison oak, and even nuts like cashews and pistachios. — Sarah Moore, Freep.com, 10 July 2026

This member of the Anacardaceae family, which also includes poison oak and poison sumac, contains an oil resin that causes a horribly itchy and bumpy rash on your skin that's tough to kick. — Caroline Biggs, Martha Stewart, 23 May 2026

But remember that on poison oak and poison ivy, the top leaf will always have a longer stem. — New York Times, 16 May 2026

Hikers or runners should watch for poison oak, ticks, rattlesnakes or hazardous trail conditions. — Don Sweeney, Sacbee.com, 12 May 2026

Word History

First Known Use

1739, in the meaning defined at sense 1

Rhymes for poison oak

• artichoke
• nanticoke
• womenfolk
• awoke
• baroque
• bespoke
• colloque
• convoke
• evoke
• invoke
• keystroke
• kinfolk

Kids Definition

poison oak

noun

: any of several shrubby plants related to poison ivy and causing a similar rash

Medical Definition

poison oak

noun

-ˈōk 

1

: any of several plants included in the genus Toxicodendron that produce an irritating oil like that of poison ivy:

a

: a bushy plant (T. diversilobum synonym R. diversiloba) of the Pacific coast

b

: a bushy plant (T. pubescens synonym R. toxicodendron) of the southeastern United States

2

: poison ivy sense 1a

3

: a skin rash produced by poison oak