The term Outside 4U City is used to describe the barren wasteland that surrounds the City.
Outside 4U City pretty much refers to the entire world other than 4U City itself. The area immediately surrounding 4U City at least is a barren wasteland with no vegetation or fauna to be seen and is inundated with near-constant rainfall. The only people/things that live here are the Outsiders, and it is unknown how they survive in the harsh environment. When on patrol outside the City the REA-5 squads carry their own DFAs rather than Universal Guns because of the nature of the region's inhabitants. As far as anyone knows the entire planet outside of 4U City is a sparsely (if at all) populated wasteland with no life to be found.