A vessel powered by an integral steam engine and used for the carriage of mail (and commonly also passengers), typically along set routes and in accordance with a published timetable. Vessels of this type were commonly built for speed (with fine lines) and were on occasion operated by the Admiralty, being naval-manned and/or lightly armed. The term remained in anachronistic use after the type was superseded, the concept being revived as Royal Mail Ship (RMS).
