The Collaborative International Dictionary of English v.0.48:

Impurity \Im*pu"ri*ty\, n.; pl. Impurities . [L. impuritas: cf.
   F. impuret['e].]
   [1913 Webster]
   1. The condition or quality of being impure in any sense;
      defilement; foulness; adulteration.
      [1913 Webster]

            Profaneness, impurity, or scandal, is not wit.
                                                  --Buckminster.
      [1913 Webster]

   2. That which is, or which renders anything, impure; foul
      matter, action, language, etc.; a foreign ingredient.
      [1913 Webster]

            Foul impurities reigned among the monkish clergy.
                                                  --Atterbury.
      [1913 Webster]

   3. (Script.) Lack of ceremonial purity; defilement.
      [1913 Webster]

WordNet (r) 3.0 (2006):

impurity
    n 1: worthless or dangerous material that should be removed;
         "there were impurities in the water" [syn: impurity,
         dross]
    2: the condition of being impure [syn: impurity, impureness]
       [ant: pureness, purity]

Moby Thesaurus II by Grady Ward, 1.0:

163 Moby Thesaurus words for "impurity":
   Gothicism, adulteration, amorality, backsliding, bad taste,
   barbarism, barbarousness, black sheep, blemish, bombasticness,
   cacology, cacophony, carnality, clumsiness, coarseness,
   contaminant, contamination, corruption, criminality, crudeness,
   cumbrousness, defectibility, defectiveness, deficiency, defilement,
   degeneration, delinquency, depravity, dinginess, dirt, dirtiness,
   dissoluteness, dysphemism, erroneousness, evil, evil nature,
   fallibility, faultiness, filth, filthiness, foreign body,
   foreign intruder, foulness, gracelessness, griminess, grossness,
   grubbiness, harshness, heaviness, ill-balanced sentences,
   immaturity, immorality, immundity, impairment, imperfection,
   impropriety, impurities, inaccuracy, inadequacy, inadequateness,
   incompleteness, inconcinnity, incorrectness, indecency,
   indecorousness, inelegance, inelegancy, inexactitude, inexactness,
   infelicity, intruder, lack, lack of finish, lack of polish,
   lasciviousness, leadenness, lecherousness, lewdness,
   libidinousness, licentiousness, looseness, lubricity, lust,
   lustfulness, maculacy, mediocrity, messiness, miriness, misfit,
   monkey wrench, moral delinquency, mote, muddiness, obscenity,
   oddball, patchiness, peccability, pollution, pompousness,
   ponderousness, poor diction, prodigality, promiscuity,
   promiscuousness, prurience, recidivism, roughness, rudeness,
   salaciousness, scruffiness, sesquipedalianism, sesquipedality,
   shortage, shortcoming, sinfulness, sketchiness,
   slipshod construction, sliver, slovenliness, smut, soiledness,
   speck, splinter, stiltedness, stone, sulliedness, taintedness,
   tastelessness, turgidity, unangelicalness, unchasteness,
   unchastity, uncleanliness, uncleanness, uncouthness, undevelopment,
   uneuphoniousness, unevenness, ungodliness, ungoodness,
   ungracefulness, unmorality, unperfectedness, unpureness,
   unrefinement, unrighteousness, unsaintliness, unseemliness,
   unsoundness, untidiness, unvirtuousness, unwieldiness, vice,
   viciousness, vileness, vulgarism, vulgarity, want, wantonness,
   waywardness, weed, wickedness, wrongdoing