The Collaborative International Dictionary of English v.0.48:

Cacophony \Ca*coph"o*ny\, n.; pl. Cacophonies. [Gr. ?????????;
   kako`s bad + ???? sound: cf. F. Cacophonie.]
   1. (Rhet.) An uncouth or disagreable sound of words, owing to
      the concurrence of harsh letters or syllables.
      "Cacophonies of all kinds." --Pope.
      [1913 Webster]

   2. (Mus.) A combination of discordant sounds.
      [1913 Webster]

   3. (Med.) An unhealthy state of the voice.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cacophony
    n 1: a loud harsh or strident noise [syn: blare, blaring,
         cacophony, clamor, din]
    2: loud confusing disagreeable sounds

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "cacophony":
   Babel, Gothicism, agitation, atonalism, atonality, bad taste,
   barbarism, barbarousness, bedlam, bluster, bombasticness, brawl,
   broil, brouhaha, cacology, chaos, clinker, clumsiness, coarseness,
   commotion, confusion of tongues, cracked voice, crudeness,
   cumbrousness, defacement, discord, discordance, discordancy,
   disfigurement, disharmony, dissonance, dissonancy, dissonant chord,
   disturbance, dryness, dysphemism, ebullition, embroilment,
   fanaticism, ferment, flap, flatness, fomentation, foofaraw, frenzy,
   fume, furor, furore, fury, fuss, gracelessness, grossness,
   gruffness, gutturalism, gutturality, gutturalness, harshness,
   heaviness, hell, hoarseness, homeliness, hubbub, huskiness,
   ill-balanced sentences, ill-favoredness, impropriety, impurity,
   inconcinnity, incorrectness, indecorousness, inelegance,
   inelegancy, infelicity, inharmoniousness, inharmony,
   lack of finish, lack of polish, leadenness, noise, off note,
   pandemonium, passion, plainness, pompousness, ponderousness,
   poor diction, racket, rage, raspiness, raucity, roughness, row,
   ruckus, rudeness, rumpus, scrapiness, scratchiness,
   sesquipedalianism, sesquipedality, shapelessness, sharpness,
   slipshod construction, sour note, sourness, static, stertorousness,
   stiltedness, storminess, stridor, tastelessness, tempestuousness,
   thickness, throatiness, tumult, tumultuousness, tunelessness,
   turbulence, turgidity, turmoil, uglification, uglifying, ugliness,
   unaestheticness, unattractiveness, unbeautifulness, uncomeliness,
   uncouthness, uneuphoniousness, ungainliness, ungracefulness,
   unhandsomeness, unharmoniousness, unloveliness, unmusicality,
   unpleasingness, unprettiness, unrefinement, unseemliness,
   unshapeliness, unsightliness, untunefulness, unwieldiness, uproar,
   upset, vulgarism, vulgarity, wildness, wolf, zeal, zealousness