Literally means "young men" in Arabic, but is commonly used to refer to "the boys". In Dubai it is used to refer to your boys, or eg. homies, gang, posse, clique. It is used also to refer to the people who will back you up in a fight.
"Ohh you wanna mess around now? I'll bring my shabaab!!" or "Don't fuck with me, i know half the shabaab of Dubai!"