A trend with a lot of currency right now. It means that something has a sort of futuristic look, but it's the kind of future that was imagined in the 50s and 60s, as in The Jetsons.

Use it: That shiny, silver bag is so retro. But, oh, it's kind of futuristic and space-age as well.
Wow, that must be the retro-futurism I've been hearing all about.

source: NZ Herald News