corvette

(historical) A flush-decked warship of the 17th-18th centuries having a single tier of guns; it ranked next below a frigate; – called in the United States navy a sloop of war.
In a modern navy, a lightly armed and armoured blue water warship, smaller than a frigate, capable of transoceanic duty.
(broadly) In a modern navy, a lightly armed and armoured blue water warship, smaller than a frigate, capable of transoceanic duty.