1. Capable of being irriated.

2. Very susceptible of anger or passion; easily inflamed or exasperated; as, an irritable temper. "Vicious, old, and irritable." (Tennyson)

3. <physiology> Endowed with irritability; susceptible of irritation; capable of being excited to action by the application of certain stimuli.

4. <medicine> Susceptible of irritation; unduly sensitive to irritants or stimuli. See Irritation.

Synonyms: Excitable, irascible, touchy, fretful, peevish.

Origin: L. Irritabilis: cf. F. Irritable. See Irritate.

(01 Mar 1998)