Synonyms for Irritable (same or very similar meaning)
WordNet sense 1 (capable of responding to stimuli):
excitableWordNet sense 2 (responsive to physical stimuli):
sensitiveWordNet sense 3 (easily irritated or annoyed):
cranky, fractious, nettlesome, peevish, pettish, petulant, scratchy, testy, peckish, techy, tetchyFrom the ODE community, based on WordNetadd/edit