As used in this chapter unless the context clearly requires otherwise:

(1) "Department" means the department of licensing;

(2) "Motor fuel" means all combustible gases and liquids used for the generation of power for propulsion of motor vehicles;

(3) "Motor carrier" means an individual, partnership, firm, association, or private or public corporation engaged in interstate commercial operation of motor vehicles, any part of which is within this state or any other state which is party to an agreement under this chapter;

(4) "State" means a state, territory, or possession of the United States, the District of Columbia, a foreign country, or a state or province of a foreign country;

(5) "Base state" means the state in which the motor carrier is legally domiciled, or in the case of a motor carrier who has no legal domicile, the state from or in which the motor carrier's vehicles are most frequently dispatched, garaged, serviced, maintained, operated, or otherwise controlled;

(6) "Agreement" means a motor fuel tax agreement under this chapter;

(7) "Licensee" means a motor carrier who has been issued a fuel tax license under a motor fuel tax agreement.