The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

postulant
    n 1: one submitting a request or application especially one
         seeking admission into a religious order

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "postulant":
   abbess, abecedarian, alphabetarian, applicant, apprentice,
   articled clerk, aspirant, beginner, bidder, boot, candidate,
   canoness, catechumen, claimant, clergywoman, conventual, debutant,
   entrant, fledgling, freshman, greenhorn, ignoramus, inductee,
   initiate, lady superior, mother superior, neophyte, new boy,
   newcomer, novice, novitiate, nun, petitioner, prioress,
   probationer, probationist, raw recruit, recruit, religieuse,
   rookie, secular canoness, seeker, sister, solicitant, solicitor,
   suitor, superioress, suppliant, supplicant, tenderfoot,
   the reverend mother, tyro