anything that irritates.
Physiology, Pathology. a biological, chemical, or physical agent that stimulates a characteristic function or elicits a response, especially an inflammatory response.
Origin of irritant
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
causing irritation; irritating
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
1630s, from Latin irritantem (nominative irritans), present participle of irritare (see irritate). As a noun, from 1802.
Online Etymology Dictionary, © 2010 Douglas Harper
Causing irritation, especially physical irritation.
A source of irritation.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.