1. any of the early patriarchs who lived prior to the Deluge

2. a very old (or old fashioned) person

1. of or relating to the period before the Biblical flood;

"Antediluvian man"

2. so extremely old as seeming to belong to an earlier period;

"a ramshackle antediluvian tenement"

"antediluvian ideas"

"archaic laws"