Is it ensure, insure, or assure?
one of the two principal types of merchant ships as classified by operating method (the other is the ocean liner). The tramp steamer, in contrast to the liner, operates without a schedule, going wherever required to deliver its cargoes. The tramp is a descendant of the early merchant ships whose masters (who were also their owners) loaded them with cargo at home to sell abroad, and vice versa. Tramps are used mainly for carrying bulk commodities or homogeneous cargoes in whole shiploads, with each voyage separately negotiated between the ship's owner and the shipper, usually through a broker.