tonnage

noun

1. the capacity of a merchant vessel, expressed either in units of weight, as deadweight tons, or of volume, as gross tons.
2. ships collectively considered with reference to their carrying capacity or together with their cargoes.
3. a duty on ships or boats at so much per ton of cargo or freight, or according to the capacity in tons.

noun

1. the capacity of a merchant ship expressed in tons, for which purpose a ton is considered as 40 cubic feet of freight or 100 cubic feet of bulk cargo, unless such an amount would weigh more than 2000 pounds in which case the actual weight is used
2. the weight of the cargo of a merchant ship
3. the total amount of shipping of a port or nation, estimated by the capacity of its ships
4. a duty on ships based either on their capacity or their register tonnage