Source : Webster's Revised Unabridged Dictionary (1913)

Postulant \Pos"tu*lant\ (?; 135), n. [F., fr. L. postulans, p.
   pr. of postulare. See {Postulate}.]
   One who makes a request or demand; hence, a candidate.

Source : WordNet®

postulant
     n : one submitting a request or application especially one
         seeking admission into a religious order