A special handbag kept close at hand, complete with fresh knickers and toothbrush for one night stands. (i.e inpromptu sexual encounters following a night out)
She grabbed her slagbag from beneath her desk before heading out on the pull last friday.
Person A: Hey did you hear about that girl from the floor above? She started making out with another guy while her boyfriend was there!
Person B: I know! She's such a slagbag!
A slagbag is an insult that sounds really offensive but actually does not mean very much. According to dictionary.com, slag is the vitreous mass left as a residue by the smelting of metallic ore.