The Collaborative International Dictionary of English v.0.48:

Unclean \Un*clean"\ ([u^]n*kl[=e]n"), a. [AS. uncl[=ae]ne. See
   Unnot, and Clean.]
   1. Not clean; foul; dirty; filthy.
      [1913 Webster]

   2. Ceremonially impure; needing ritual cleansing.
      [1913 Webster]

            He that toucheth the dead body of any man shall be
            unclean seven days.                   --Num. xix.
                                                  11.
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   3. Morally impure. "Adultery of the heart, consisting of
      inordinate and unclean affections." --Perkins.
      [1913 Webster] -- Un*clean"ly, adv. -- Un*clean"ness,
      n.
      [1913 Webster]

   Unclean animals (Script.), those which the Israelites were
      forbidden to use for food.

   Unclean spirit (Script.), a wicked spirit; a demon. --Mark
      i. 27.
      [1913 Webster]

WordNet (r) 3.0 (2006):

uncleanness
    n 1: the state of being unsanitary [syn: dirtiness,
         uncleanness] [ant: cleanness]