noun the weight of goods carried in a boat or a ship.
2. tonnage ·noun the whole amount of shipping estimated by tons; as, the tonnage of the united states. ·see ton.
3. tonnage ·noun a duty or impost on vessels, estimated per ton, or, a duty, toll, or rate payable on goods per ton transported on canals.
4. tonnage ·noun the cubical content or burden of a vessel, or vessels, in tons; or, the amount of weight which one or several vessels may carry. ·see ton, ·noun (b).