The Collaborative International Dictionary of English v.0.48:

Irascibility \I*ras`ci*bil"i*ty\, n. [Cf. F. irascibilit['e].]
   The quality or state of being irascible; irritability of
   temper; irascibleness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

irascibility
    n 1: a feeling of resentful anger [syn: irascibility, short
         temper, spleen, quick temper]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "irascibility":
   aggressiveness, agitability, bearishness, bellicosity,
   belligerence, bickering, bitchiness, cantankerousness,
   churlishness, combativeness, combustibility, contentiousness,
   contrariness, crabbedness, crankiness, crossness, crustiness,
   cussedness, difficultness, disagreeability, dissension, dissent,
   dissidence, dourness, edginess, emotional instability,
   emotionalism, eruptiveness, excitability, excitableness,
   explosiveness, faction, factiousness, flak, fractiousness,
   frowardness, huffiness, huffishness, infighting, inflammability,
   irritability, latent violence, litigiousness, meanness,
   nervousness, orneriness, partisan spirit, partisanship,
   perturbability, perverseness, perversite, perversity, prickliness,
   pugnacity, quarrelsomeness, sensitivity, shrewishness,
   skittishness, snappishness, startlishness, stuffiness, sulkiness,
   sullenness, tempestuousness, testiness, touchiness, ugliness,
   violence, waspishness, waywardness, wrongheadedness