a poisonous, irritant liquid, CHO, present in poison ivy, poison sumac, etc.
See urushiol in American Heritage Dictionary 4
(o͝o-ro͞oˈshē-ôlˌ, -ōlˌ, -ŏlˌ)
noun
A toxic substance present in the resin or on the surface of plants of the genus Rhus, including poison ivy and the lacquer tree, from which a black Japanese lacquer is obtained.