irritable in WordNet English dictionary

1. easily irritated or annoyed
   "an incorrigibly fractious young man"; "not the least nettlesome of his countrymen"
   cranky  fractious  irritable  nettlesome  peevish  peckish  pettish  petulant  scratchy  testy  tetchy  techy 
   
2. capable of responding to stimuli
   excitable  irritable 
   
3. abnormally sensitive to a stimulus
   irritable