[ oo-roo-shee-awl, -ol ]
/ ʊˈru ʃiˌɔl, -ˌɒl /


a toxic, liquid, catechol derivative, the active irritant principle in several species of the plant genus Rhus, as in poison ivy.

Nearby words

  1. uruk,
  2. urumchi,
  3. urumiyeh,
  4. urundi,
  5. urus,
  6. us,
  7. us customary system,
  8. usa,
  9. usable,
  10. usaf

Origin of urushiol

1910–15; < Japanese urushi lacquer + -ol1

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for urushiol


/ (ˈuːrʊʃɪˌɒl, uːˈruː-) /


a poisonous pale yellow liquid occurring in poison ivy and the lacquer tree

Word Origin for urushiol

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

Medicine definitions for urushiol


[ u-rōōshē-ôl′, -ōl′ ]


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.

Science definitions for urushiol


[ u-rōōshē-ôl′, -ōl′ ]

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.