The Collaborative International Dictionary of English v.0.48:

Antenuptial \An`te*nup"tial\, a.
   Preceding marriage; as, an antenuptial agreement. --Kent.
   [1913 Webster]

WordNet (r) 3.0 (2006):

antenuptial
    adj 1: relating to events before a marriage; "prenuptial
           agreement" [syn: prenuptial, premarital,
           antenuptial] [ant: postnuptial]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

ANTE-NUPTIAL. What takes place before marriage; as, an ante-nuptial
agreement, which is an agreement made between a man and a woman in
contemplation of marriage. Vide Settlement.