noun (n)

• the psychological state of being irritated or annoyed(noun.state)

  Synonym:
  annoyance, botheration, vexation
  

  source: wordnet30
• a sudden outburst of anger(noun.feeling)

  Synonym:
  pique, temper
  

  source: wordnet30
• (pathology) abnormal sensitivity to stimulation(noun.state)

  Example:
  Any food produced irritation of the stomach.
  

  source: wordnet30
• the neural or electrical arousal of an organ or muscle or gland(noun.state)

  Synonym:
  excitation, innervation
  

  source: wordnet30
• an uncomfortable feeling of mental painfulness or distress(noun.feeling)

  Synonym:
  discomfort, soreness
  

  source: wordnet30
• unfriendly behavior that causes anger or resentment(noun.act)

  Synonym:
  aggravation, provocation
  

  source: wordnet30
• the act of troubling or annoying someone(noun.act)

  Synonym:
  annoyance, annoying, vexation
  

  source: wordnet30
• The act of irritating, or exciting, or the state of being irritated; excitement; stimulation, usually of an undue and uncomfortable kind; especially, excitement of anger or passion; provocation; annoyance; anger.(noun)

  source: webster1913