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. (Science: physiology) Endowed with irritability; susceptible of irritation; capable of being excited to action by the application of certain stimuli.
4. (Science: medicine) susceptible of irritation; unduly sensitive to irritants or stimuli. See irritation.
Synonym: excitable, irascible, touchy, fretful, peevish.
Origin: L. Irritabilis: cf. F. Irritable. See irritate.