The Collaborative International Dictionary of English v.0.48:

Exasperation \Ex*as`per*a"tion\, n. [L. exasperatio: cf. F.
   exasp['e]ration.]
   1. The act of exasperating or the state of being exasperated;
      irritation; keen or bitter anger.
      [1913 Webster]

            Extorted from him by the exasperation of his
            spirits.                              --South.
      [1913 Webster]

   2. Increase of violence or malignity; aggravation;
      exacerbation. "Exasperation of the fits." --Sir H. Wotton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

exasperation
    n 1: an exasperated feeling of annoyance [syn: aggravation,
         exasperation]
    2: actions that cause great irritation (or even anger)

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "exasperation":
   aggravation, agitation, amplification, animation, annoyance,
   annoyingness, arousal, arousing, augmentation, bad news,
   bedevilment, besetment, bore, bother, botheration, bothersomeness,
   contentiousness, crashing bore, deepening, deliberate aggravation,
   deterioration, devilment, difficulty, disapprobation, disapproval,
   discontent, displeasure, dissatisfaction, dogging, downer, drag,
   electrification, embittering, embitterment, enhancement,
   enlargement, exacerbation, excitation, excitement, exhilaration,
   firing, fomentation, galvanization, harassment, harrying, headache,
   heightening, hounding, incitation, incitement, increase,
   inflammation, infuriation, instigation, intensification,
   irksomeness, irritant, irritation, lathering up, magnification,
   molestation, nuisance, pep rally, pep talk, persecution,
   perturbation, peskiness, pest, pester, pestiferousness, plague,
   plaguesomeness, pother, problem, provocation, provokingness,
   rabble-rousing, resentfulness, resentment, sharpening, souring,
   steaming up, stimulation, stimulus, stirring, stirring up,
   stirring-up, tiresomeness, trial, trouble, troublesomeness,
   vexation, vexatiousness, wearisomeness, whipping up, working up,
   worriment, worrisomeness, worry, worsening