From The Collaborative International Dictionary of English v.0.48 [gcide]:
Unlike \Un*like"\, a.
1. Not like; dissimilar; diverse; having no resemblance; as,
the cases are unlike.
[1913 Webster]
2. Not likely; improbable; unlikely. [Obsoles.]
[1913 Webster]
Unlike quantities (Math.), quantities expressed by letters
which are different or of different powers, as a, b, c,
a^2, a^3, x^n, and the like.
Unlike signs (Math.), the signs plus (+) and minus (-).
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
unlike
adj 1: marked by dissimilarity; "for twins they are very
unlike"; "people are profoundly different" [syn:
unlike, dissimilar, different] [ant: like,
similar]
2: not equal in amount; "they distributed unlike (or unequal)
sums to the various charities" [ant: like, same]