The Collaborative International Dictionary of English v.0.48:

Anterior \An*te"ri*or\, a. [L. anterior, comp. of ante before.]
   1. Before in time; antecedent.
      [1913 Webster]

            Antigonus, who was anterior to Polybius. --Sir G. C.
                                                  Lewis.
      [1913 Webster]

   2. Before, or toward the front, in place; as, the anterior
      part of the mouth; -- opposed to posterior.
      [1913 Webster]

   Note: In comparative anatomy, anterior often signifies at or
         toward the head, cephalic; and in human anatomy it is
         often used for ventral.
         [1913 Webster]

   Syn: Antecedent; previous; precedent; preceding; former;
        foregoing.
        [1913 Webster]

WordNet (r) 3.0 (2006):

anterior
    adj 1: of or near the head end or toward the front plane of a
           body [ant: posterior]
    2: earlier in time [syn: anterior, prior(a)]
    n 1: a tooth situated at the front of the mouth; "his
         malocclusion was caused by malposed anteriors" [syn: front
         tooth, anterior]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "anterior":
   album, ana, analects, antecedent, anticipatory, chief, ci-devant,
   collection, compilation, delectus, earlier, early, elder, exordial,
   first, florilegium, fore, foregoing, forehand, foremost, former,
   forward, front, frontal, garland, head, headmost, inaugural,
   initiatory, leading, miscellany, older, omnibus, posy, precedent,
   preceding, precessional, precurrent, precursory, preexistent,
   prefatory, preliminary, preludial, prelusive, preparatory,
   prevenient, previous, primary, prime, prior, proemial,
   propaedeutic, senior, treasure-house, treasury