What Does It Mean?

You are correct!

From our dictionary:
an•te•di•lu•vi•an

(an"tE•di•lOO'vEun),
adj.
1. of or belonging to the period before the Flood. Gen. 7, 8.
2. very old, old-fashioned, or out of date; antiquated; primitive: antediluvian ideas.

n.
1. a person who lived before the Flood.
2. a very old or old-fashioned person or thing.