Source : Webster's Revised Unabridged Dictionary (1913)

Unbeliever \Un`be*liev"er\, n.
   1. One who does not believe; an incredulous person; a
      doubter; a skeptic.

   2. A disbeliever; especially, one who does not believe that
      the Bible is a divine revelation, and holds that Christ
      was neither a divine nor a supernatural person; an
      infidel; a freethinker.

   Syn: See {Infidel}.

Source : WordNet®

unbeliever
     n : someone who refuses to believe (as in a divinity) [syn: {disbeliever},
          {nonbeliever}]