has caught wind of a new trend - that started out of Atlanta. Men are not only sagging their pants . . . they're sagging their underwear too - exposing their bare butts.

It's not clear WHERE this style began, but it's reportedly catching on among teenagers in the hood.

What do YOU GUYS think of this - should it even be LEGAL for boys to have their BARE BUTTS out in public??

Here is a link to the video