a poisonous, irritant liquid, CHO, present in poison ivy, poison sumac, etc.
Origin:
Jpn urushi, lac tree, lacquer + -ol: coined (1907) by Toshiyuki Mashima, who isolated it
See urushiol in American Heritage Dictionary 4
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.