When a girl has a wallet, phone, pack of cigarettes, etc. in the back pocket of her tight-fitting jeans, thus causing an odd protrusion from her butt.
Jamie: Man, if that girl is gonna wear such tight jeans she better upgrade to a smaller phone!
Christina: Yeah, shes got some seriousss lump ass!
Translates to "are you dee one too see four dee bee jay". If that isn't obvious enough, I'm very sorry for you.