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!
Christina: Yeah, shes got some seriousss lump ass!
by Nathan T April 1, 2008
by fatassfag January 25, 2005