/abu grEb/ with a as in father, b as in byte, u as in tutor, g as in geld, r as in preen, E as in get, and b as in byte once more. But then I don't speak Arabic.

The gh in Arabic is a voiced velar fricative. English doesn't have this sound, but it's similar to the ch in the German pronunciation of Bach, but with your glottis vibrating. If you wish to hear an Arab say the name, listen here:

http://slate.msn.com/id/2100290/