Turret ships were a 19th century type of warship, the earliest to have their guns mounted in a revolving turret, instead of a broadside arrangement.
First ship of the type was HMS Trusty, although USS Monitor is more famous. Another example was HMS Captain of 1869, which was unstable and capsized after just a few months in operation.
Turret ship may be found applied to a type of late 19th century commercial steam vessel designed to minimize Suez Canal fees that were based on deck area. Turret Deck Ship is a more precise term for these vessels.