An officer of Customs in the Port of London, whose duty it was to visit and make a return of coasting vessels trading from one part of the kingdom to another, and which (from the nature of their cargo) were not required to report or make entry at the Custom House. These vessels were liable to the payment of certain small dues, which it was the duty of the Coasting Waiter to exact. He was also expected to search the cargo, that no contraband goods were illicitly on board. Like Tide Waiters, these Coasting Waiters were abolished in the latter half of the nineteenth century, and their duties have since been performed by the Examining Officer. Their salary was about 40 a year.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894