Being rich as fuck, ballin' outta control. Racks is a synonym for stacks; a stack being $1,000. Basically, if you stackin' money crazy high, you got racks on racks on racks. Made famous by Yung Chris' hit song 'Racks'.
That nigga Yung Chris might not have had racks on racks on racks before that song, but that shit is a hit, I bet he's rollin' now.