The Collaborative International Dictionary of English v.0.48:

antediluvian \an`te*di*lu"vi*an\
   ([a^]n`t[-e]*d[i^]*l[=u]"v[i^]*an), a.
   Of or relating to the period before the Deluge in Noah's
   time; hence, antiquated; as, an antediluvian vehicle. -- n.
   One who lived before the Deluge.
   [1913 Webster]

WordNet (r) 3.0 (2006):

antediluvian
    adj 1: of or relating to the period before the biblical flood;
           "antediluvian man" [syn: antediluvian, antediluvial]
    2: so extremely old as seeming to belong to an earlier period;
       "a ramshackle antediluvian tenement"; "antediluvian ideas";
       "archaic laws" [syn: antediluvian, antiquated, archaic]
    n 1: any of the early patriarchs who lived prior to the Noachian
         deluge [syn: antediluvian, antediluvian patriarch]
    2: a very old person [syn: ancient, antediluvian]