1. The quality or state of being irritable.
  2. Quick excitability to annoyance, impatience, or anger.
  3. Abnormal or excessive excitability of an organ or part of the body.
  4. The property of protoplasm and of living organisms that permits them to react to stimuli.

The emotion of Irritability is found in the Liver meridian in the Wood element.

Definition from Dictionary by Merriam-Webster.