Unlike \Un*like"\, a.

1. Not like; dissimilar; diverse; having no resemblance; as, the cases are unlike.

2. Not likely; improbable; unlikely. [Obsoles.]

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 (-).

Source: Webster's Revised Unabridged Dictionary (1913)