tonnage duty

A charge imposed on a commercial vessel for entering, remaining in, or leaving a port, usu. assessed on the basis of the ship’s weight. • U.S. Const. art. I, § 10, cl. 3 prohibits the states from levying tonnage duties. — Also termed tonnage tax; tonnage. [Cases: Commerce 78; Shipping 7. C.J.S. Commerce § 120; […]