ir·ri·ta·ble / ˈiritəbəl/ • adj. having or showing a tendency to be easily annoyed or made angry: she was tired and irritable. ∎ Med. (of a bodily part or organ) abnormally sensitive. ∎ Med. (of a condition) caused by such sensitivity. ∎ Biol. (of a living organism) having the property of responding actively to physical stimuli.DERIVATIVES: ir·ri·ta·bil·i·ty / ˌiritəˈbilitē/ n.ir·ri·ta·bly / -blē/ adv.