ir•ri•tantPronunciation: (ir'i-tnt), [key]
tending to cause irritation; irritating.
anything that irritates.
2. Physiol., Pathol.
a biological, chemical, or physical agent that stimulates a characteristic function or elicits a response, esp. an inflammatory response.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.