Source : Webster's Revised Unabridged Dictionary (1913)

Unlikeness \Un*like"ness\, n.
   The quality or state of being unlike; want of resemblance;
   dissimilarity. --Tennyson.

Source : WordNet®

unlikeness
     n : dissimilarity evidenced by an absence of likeness [syn: {dissimilitude}]
         [ant: {likeness}, {likeness}]