From WordNet (r) 2.0 (August 2003) [wn]:
irascible
adj 1: quickly aroused to anger; "a hotheaded commander" [syn:
choleric, hotheaded, hot-tempered,
quick-tempered, short, short-tempered]
2: characterized by anger; "a choleric outburst"; "an irascible
response" [syn: choleric]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Irascible \I*ras"ci*ble\, a. [L. irascibilis, fr. irasci to be
angry, ira anger: cf. F. irascible. See Ire.]
Prone to anger; easily provoked or inflamed to anger;
choleric; irritable; as, an irascible man; an irascible
temper or mood. -- I*ras"ci*ble*ness, n. -- I*ras"ci*bly,
adv.
[1913 Webster]