'Irritable' definitions:

Definition of 'irritable'

From: WordNet
adjective
Easily irritated or annoyed; "an incorrigibly fractious young man"; "not the least nettlesome of his countrymen" [syn: cranky, fractious, irritable, nettlesome, peevish, peckish, pettish, petulant, scratchy, testy, tetchy, techy]
adjective
Abnormally sensitive to a stimulus
adjective
Capable of responding to stimuli [syn: excitable, irritable]

Definition of 'Irritable'

From: GCIDE
  • Irritable \Ir"ri*ta*ble\, a. [L. irritabilis: cf. F. irritable. See Irritate.] [1913 Webster]
  • 1. Capable of being irritated. [1913 Webster]
  • 2. Very susceptible of anger or passion; easily inflamed or exasperated; as, an irritable temper. [1913 Webster]
  • Vicious, old, and irritable. --Tennyson. [1913 Webster]
  • 3. (Physiol.) Endowed with irritability; susceptible of irritation; capable of being excited to action by the application of certain stimuli. [1913 Webster]
  • 4. (Med.) Susceptible of irritation; unduly sensitive to irritants or stimuli. See Irritation, n., 3.
  • Syn: Excitable; irascible; touchy; fretful; peevish. [1913 Webster]