The word for word definition of this is what is your religion, but the manyeks of Fuck Barca use this as a phrase which generally means what the fuck are you saying. When something really outlandish is said you use Shu deen rabak.
Zoran: Barcelona is the best team in the world
Alek: Bro shu deenak, they stink
Kassem: Yuppp
Zoran: Messi is the best player in the world
Kassem: Nigga shu deen rabak, he’s a stinker
Hamade: OMGGGGGGGG
Adam: Yo where’s Fufu