Webster's Revised Unabridged Dictionary · 1913

Irritable

Irritable , adjective

[Latin irritabilis: compare French irritable. See Irritate.]

1.
Capable of being irritated.
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, n., 3.