WordNet (r) 3.0 (2006):

unalike
    adj 1: not alike or similar; "as unalike as two people could be"
           [syn: unalike, dissimilar] [ant: alike(p), like,
           similar]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "unalike":
   contrasting, counter, different, disparate, dissimilar, divergent,
   diverse, hardly like, nonuniform, odd, off, offbeat, out,
   scarcely like, unequal, unidentical, unlike, unmatched,
   unresembling, unsame, unsimilar, various