Unloaded Vehicle Weight (UVW) is the weight of a vehicle as manufactured at the factory. It includes full engine and generator fuel tanks and fluids, if applicable. It does not include cargo, water, p [..]

Weight of the vehicle without manufacturer's or dealer-installed options and before adding fuel, water or supplies.

49CFR 571 definition of UVW is:
Unloaded vehicle weight mean the weight of a vehicle with maximum capacity of all the fluids necessary for operation of the vehicle, but without cargo, occupants, or accessories that are ordinarily removed from the vehicle when they are used.