Privateer

A privateer was a privately-owned ship that was given an official government letter of marque to raid enemy shipping during wartime. The term also applies to sailors on such ships.

Well-known privateers included Francis Drake and Martin Frobisher, both from England.

United States
During the American Revolution, privateers were used by the United States to raid British shipping.Summary of Service of N.H. Privateer "General Sullivan" at 

additional links of interest:
1847 obituary of "General Sullivan: Crewman mentions his capture 1779 by the "RoebucK"
 Also reported capture of "Charlotte" by General Sullivan"

During the War of 1812, privateers were again used to raid British shipping.

During the American Civil War, the Confederate States issued privateers letters of marque.

 References