noun

1. The state or quality of being irritable; quick excitability

   “irritability of temper”

2. A natural susceptibility, characteristic of all living organisms, tissues, and cells, to the influence of certain stimuli, response being manifested in a variety of ways.

3. A condition of morbid excitability of an organ or part of the body; undue susceptibility to the influence of stimuli.

Synonyms: fretfulness, petulance