QBAB simply means, "Quit Being A Bitch". Coined by Travis and Rudy from The Cavaliers D&BC, the phrase has been carried into popularity after only a week into existence by social media sites such as Facebook and MySpace. It is usually used when someone is complaining about something. There is no wrong time to use the phrase. It may also be used as, "DBAB", which means, "Don't Be A Bitch". Both are acceptable.
"Dang, these jazz-running basics are kicking me in the ass!"