ply verb definition in Train and bus travel topic from the Oxford Advanced Learner's Dictionary

ply

 verb: Train and bus travel topic
[intransitive, transitive] (literary or Indian English) (of ships, buses, etc.) to travel regularly along a particular route or between two particular places + adv./prep. Ferries ply across a narrow strait to the island. The train plies twice a day between Paris and Madrid. Buses ply regularly to and from these places. ply something canals plied by gondolas and steam boats ships plying the route between Tripoli and Malta