a boat carrying artillery, a gunboat.

A boat or small vessel of light draft carrying one or more guns of large calibre; any small vessel fitted for carrying guns.

? a small ship of war.

a two-masted ship of war, now obsolete.

A fast ship mounted with guns, typically used to attack coastal targets. Cf. gunboat, n. 1a.

a ship of war with a turret (sense 2b).

= turret-ship n.

colloquial (chiefly humorous). A gun. Also: a small ship carrying guns. Now rare.