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.
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   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]