Means “Old Fasioned”.
I saw this used in the paper today. What a great word. The meaning in todays sense is generally “old fasioned” as in, an old fasioned attidude, or way of thinking.
Diluvian means flood, from deluge I guess, and ante means “before”, so the latin meaning is before the flood, apparently referring to the flood in the bible (you know, the Noah’s arc one..) So, before the flood means very old, antiquated etc..