The Collaborative International Dictionary of English v.0.48:

Harshness \Harsh"ness\, n.
   The quality or state of being harsh.
   [1913 Webster]

         O, she is
         Ten times more gentle than her father's crabbed,
         And he's composed of harshness.          --Shak.
   [1913 Webster]

         'Tis not enough no harshness gives offense,
         The sound must seem an echo to the sense. --Pope.

   Syn: Acrimony; roughness; sternness; asperity; tartness. See
        Acrimony.
        [1913 Webster]

WordNet (r) 3.0 (2006):

harshness
    n 1: the roughness of a substance that causes abrasions [syn:
         harshness, abrasiveness, scratchiness]
    2: the quality of being unpleasant (harsh or rough or grating)
       to the senses [syn: harshness, roughness]
    3: the quality of being cruel and causing tension or annoyance
       [syn: cruelty, cruelness, harshness]
    4: excessive sternness; "severity of character"; "the harshness
       of his punishment was inhuman"; "the rigors of boot camp"
       [syn: severity, severeness, harshness, rigor,
       rigour, rigorousness, rigourousness, inclemency,
       hardness, stiffness]

Moby Thesaurus II by Grady Ward, 1.0:

263 Moby Thesaurus words for "harshness":
   Babel, Gothicism, Spartanism, abominability, abruptness, acerbity,
   acidity, acidulousness, acridity, acrimony, acuteness,
   aggressiveness, animality, aphonia, artificial voice, asperity,
   astringency, atrocity, austerity, authoritarianism, bad taste,
   barbarism, barbarity, barbarousness, baseness, bearishness,
   beastliness, bite, bitingness, bitterness, bloodlust, bluntness,
   bombasticness, boorishness, brashness, broken speech, broken tones,
   broken voice, brusqueness, brusquerie, brutality, bumpiness,
   cacology, cacophony, causticity, childish treble, choked voice,
   choppiness, churlishness, clamor, clash, clumsiness, coarseness,
   contemptibility, contrariety, cracked voice, cragginess, croak,
   crow, crudeness, cruelty, crustiness, cumbrousness, curtness,
   cuttingness, demandingness, despicability, despicableness,
   destructiveness, discipline, discord, disgustingness, dryness,
   dysarthria, dyslalia, dyslogia, dysphasia, dysphemism, dysphonia,
   dysphrasia, edge, exactingness, extremity, falsetto, ferociousness,
   fierceness, flintiness, force, foulness, fulsomeness, furiousness,
   gracelessness, granulation, grimness, grip, grossness, gruffness,
   gutturalism, gutturality, gutturalness, hardness, hatefulness,
   hawking voice, heartlessness, heaviness, heinousness, hispidity,
   hiss, hoarseness, huskiness, idioglossia, idiolalia, ignobility,
   ill-balanced sentences, impairment of speech, impetuosity,
   impropriety, impurity, inclemency, inconcinnity, incorrectness,
   indecorousness, inelegance, inelegancy, inequality, inexorableness,
   infelicity, inhumanity, intensity, irregularity, jaggedness,
   jangle, jar, joltiness, keenness, lack of finish, lack of polish,
   leadenness, lisp, lisping, loathsomeness, loss of voice, malignity,
   mercilessness, mere noise, meticulousness, mindlessness, mordacity,
   mordancy, murderousness, muzzy speech, nasal tone, nasalization,
   nastiness, nauseousness, noise, noisomeness, nonuniformity,
   noxiousness, objectionability, objectionableness, obnoxiousness,
   obscenity, odiousness, offensiveness, piquancy, pitilessness,
   poignancy, point, pompousness, ponderousness, poor diction,
   pungency, putridity, putridness, quaver, raggedness, raspiness,
   raucity, rebarbativeness, regimentation, relentlessness,
   remorselessness, repellence, repellency, repugnance, repulsiveness,
   rigid discipline, rigor, rottenness, rough air, roughness,
   rudeness, ruggedness, rugosity, ruthlessness, savagery,
   scraggliness, scrapiness, scratchiness, sesquipedalianism,
   sesquipedality, severity, shake, sharpness, short shrift,
   shortness, sibilation, slipshod construction, sourness,
   speech defect, speech impediment, sternness, stertorousness,
   stiltedness, sting, strictness, stridency, stringency, surliness,
   tartness, tastelessness, teeth, tender mercies, terrorism,
   thickness, throatiness, tooth, toughness, tremor, trenchancy,
   truculence, turbulence, turgidity, twang, ugliness,
   uncompassionateness, uncouthness, uneuphoniousness, unevenness,
   unfeelingness, unforgivingness, ungentleness, ungracefulness,
   unmercifulness, unrefinement, unremorsefulness, unseemliness,
   unsmoothness, unspeakableness, unsympatheticness, ununiformity,
   unwieldiness, unyieldingness, vandalism, vehemence, venom,
   viciousness, vileness, violence, virulence, vulgarism, vulgarity