As used in this chapter, unless the context otherwise requires:
Fuel used for an industrial purpose includes fuel used in a vehicle, engine, or machine, movable or immovable, operated in whole or in part by internal combustion. It does not include heating fuel, fuel used for an agricultural purpose, fuel used for a railroad purpose, or fuel used to operate a licensed motor vehicle.
N.D.C.C. § 57-43.1-01