Source : Webster's Revised Unabridged Dictionary (1913)

Unclean \Un*clean"\, a. [AS. uncl?ne. See {Unnot}, and {Clean}.]
   1. Not clean; foul; dirty; filthy.

   2. Ceremonially impure; needing ritual cleansing.

            He that toucheth the dead body of any man shall be
            unclean seven days.                   --Num. xix.
                                                  11.

   3. Morally impure. ``Adultery of the heart, consisting of
      inordinate and unclean affections.'' --Perkins. --
      {Un*clean"ly}, adv. -- {Un*clean"ness}, n.

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

   {Unclean spirit} (Script.), a wicked spirit; a demon. --Mark
      i. 27.

Source : WordNet®

unclean
     adj 1: soiled or likely to soil with dirt or grime; "dirty unswept
            sidewalks"; "a child in dirty overalls"; "dirty
            slums"; "piles of dirty dishes"; "put his dirty feet
            on the clean sheet"; "wore an unclean shirt"; "mining
            is a dirty job"; "Cinderella did the dirty work while
            her sisters preened themselves" [syn: {dirty}, {soiled}]
            [ant: {clean}]
     2: ritually unclean or impure; "and the swine...is unclean to
        you"-Leviticus 11:3 [syn: {impure}] [ant: {clean}]