An armed merchantman is a merchant ship equipped with guns, usually for defensive purposes, either by design or after the fact. In the days of sail, piracy and privateers, many merchantmen would be routinely armed, especially those engaging in long distance and high value trade.
HMS Alcantara and SMS Greif dueling at close range during the action of 29 February 1916
RMS Carmania sinking SMS Cap Trafalgar near the Brazilian islands of Trindade, 14 September 1914
Kormoran in 1940. During a single ship action on 19 November 1941, off the coast of Western Australia the German auxiliary cruiser Kormoran sank HMAS Sydney before being scuttled.
A merchant ship, merchant vessel, trading vessel, or merchantman is a watercraft that transports cargo or carries passengers for hire. This is in contrast to pleasure craft, which are used for personal recreation, and naval ships, which are used for military purposes.
Historical merchant trading ship: a Dutch fluyt cargo vessel from the late 17th century
Roll-on/roll-off vessel Galaxy Leader
General cargo vessel Namibia
Bulk carrier Sabrina I