The Collaborative International Dictionary of English v.0.48:

Vehemence \Ve"he*mence\, n. [L. vehementia: cf. F.
   v['e]h['e]mence.]
   [1913 Webster]
   1. The quality or state of being vehement; impetuous force;
      impetuosity; violence; fury; as, the vehemence of the
      wind; to speak with vehemence.
      [1913 Webster]

   2. Violent ardor; great heat; animated fervor; as, the
      vehemence of love, anger, or other passions.
      [1913 Webster]

            I . . . tremble at his vehemence of temper.
                                                  --Addison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

vehemence
    n 1: intensity or forcefulness of expression; "the vehemence of
         his denial"; "his emphasis on civil rights" [syn:
         vehemence, emphasis]
    2: the property of being wild or turbulent; "the storm's
       violence" [syn: ferocity, fierceness, furiousness,
       fury, vehemence, violence, wildness]

Moby Thesaurus II by Grady Ward, 1.0:

194 Moby Thesaurus words for "vehemence":
   Alecto, Megaera, Nemesis, Tisiphone, abandon, acerbity, acidity,
   acridity, acrimony, acuteness, amperage, animality, application,
   ardency, ardor, armipotence, assiduity, assiduousness, astringency,
   atrocity, authority, barbarity, beef, bite, bitterness,
   black power, bloodlust, brutality, brute force, burning rage,
   causticity, charge, charisma, clout, cogence, cogency, commitment,
   committedness, compulsion, concentration, dedication,
   destructiveness, devotedness, devotion, devoutness, diligence,
   dint, drive, duress, earnestness, ecstasy, edge, effect,
   effectiveness, effectuality, energeticalness, energy, enthusiasm,
   excitement, extremity, faith, faithfulness, ferociousness,
   fervency, fervidness, fervor, fidelity, fierceness, fieriness,
   fire, flower power, force, force majeure, forcefulness, full blast,
   full force, furious rage, furiousness, furor, fury, glow, grip,
   gusto, harshness, heart, heartiness, heat, heatedness,
   impassionedness, impetuosity, inclemency, indefatigability,
   industriousness, industry, influence, inhumanity, intensity,
   intentness, keenness, laboriousness, liveliness, loyalty,
   main force, main strength, malignity, mana, mercilessness, might,
   might and main, mightiness, mindlessness, mordacity, mordancy,
   moxie, murderousness, muscle power, passion, passionateness,
   pitilessness, pizzazz, poignancy, point, poop, potence, potency,
   potentiality, power, power pack, power structure, power struggle,
   powerfulness, prepotency, productiveness, productivity, puissance,
   pull, punch, push, rage, relentlessness, relish, resolution, rigor,
   roughness, savagery, savor, sedulity, sedulousness, seriousness,
   severity, sharpness, sincerity, sinew, soul, spirit, steam, sting,
   strength, strenuousness, stridency, stringency, strong arm,
   superiority, superpower, tartness, tearing passion, teeth,
   terrorism, the Erinyes, the Eumenides, the Furies, tirelessness,
   towering rage, trenchancy, ungentleness, unsparingness, validity,
   vandalism, venom, verve, viciousness, vigor, vim, violence,
   virility, virtue, virulence, vitality, warmth, warmth of feeling,
   wattage, weight, zeal, zealousness