(n.) - a uncomplimentary term used to describe a person, most notably a female, who is a slut *and* will likely amount to nothing in life.
John: Did you hear about Chris's new girlfriend?
David: 'Nah, what's she like?
John: She's a high-school dropout, and she's loose as hell.
David: Damn, she sound like a cumdumpsta-nothin!
John: So how's it goin' with the new gf?
Chris: Man, I dropped that ho -- she ain't nothin' but a cumdumpsta-nothin!