1. A creative insult for a person, usually a girl, who has many sexual partners. See slag
2. An actual bag filled with slags.
3. A general greeting, not meant to cause offense.
1. "Croy is such a slag-bag, she gives blow-jobs for crack behind Burger King."
2. "And then I slammed him with a slag-bag and his eye is still swollen!"
3. "Hey, you slag-bag, what's up?"