The Collaborative International Dictionary of English v.0.48:
Irritably \Ir"ri*ta*bly\, adv. In an irritable manner. [1913 Webster]WordNet (r) 3.0 (2006):
irritably adv 1: in a petulant manner; "he said testily; `Go away!'" [syn: testily, irritably, petulantly, pettishly] 2: in an irritable manner; "she had become irritably exact"