| 1. | Navy. a grade of flag officer next in rank below a rear admiral. |
| 2. | British Navy. an officer in temporary command of a squadron, sometimes over a captain on the same ship. |
| 3. | Navy. the senior captain when two or more ships of war are cruising in company. |
| 4. | (in the U.S. Navy and Merchant Marine) the officer in command of a convoy. |
| 5. | the senior captain of a line of merchant vessels. |
| 6. | the president or head of a yacht club or boat club. |