Also a Canadian term, shortened form of 'Lebanese'. Can be considered derogatory, possibly similar to 'jap'.
In the derogatory sense, it is used to refer to the stereotypical Lebanese male of highschool age - one who is often seen wearing the latest, most expensive fashion trend. The stereotype also has extremely gelled, spiked hair, and drives a 'trendy' import car (eg. 240sx, civic). The stereotypical Leb is quick to anger and to provoke arguments, will engage in physical confrontation provided he has numerous friends in close vicinity, and will stop at nothing to shift blame.
Leb: Yo cousin, check out my new ride. Wullah it has vtec.
Guy: That's a shopping cart.