Originally a Native-American word used to describe women who would be used solely for fornication by men, then tossed in the garbage like a used rag. Now-a-days, the term is used to describe women who have sex with men, make them a sandwich, and are immediately thrown out of the vicinity.
Tom: I had sex with this total slam rag yesterday
Jake: Nice man, what kind of sandwich did she make you after?
Tom: Turkey club