- a toxic, liquid, catechol derivative, the active irritant principle in several species of the plant genus Rhus, as in poison ivy.
Origin of urushiol
1910–15; < Japanese urushi lacquer + -ol1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- a poisonous pale yellow liquid occurring in poison ivy and the lacquer tree
from Japanese urushi lacquer + -ol ²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
- A toxic substance constituting the active allergen of the irritant oil present in poison ivy, poison oak, and poison sumac.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
- A toxic substance present in the resin or on the surface of plants of the genus Rhus (syn. Toxicodendron). Urushiol is a mixture of several derivatives of catechol and is the irritating substance in poison ivy.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.