From Longman Dictionary of Contemporary Englishpoison oakˌpoison ˈoak noun [uncountable] HBPa North American plant with leaves similar to an oak tree’s, that makes your skin hurt and itch if you touch it
Examples from the Corpus
poison oak• Fire officials said bee stings and poison oak were the most serious problems.• There were casualties: One soldier burned out his chain saw; another got poison oak. 