Antediluvian

"Antediluvian" means something is really, really, really old. Imagine a dinosaur from millions of years ago. That's antediluvian too! It's a big, fancy word people use when they talk about things that happened a long, long time ago, before anyone can remember. It's like talking about the time before your great-great-grandparents were born. So, when someone says something is antediluvian, they mean it's super old and probably from a time long before anyone can remember.