Definition of: lieutenant

(l·ten′ənt, Brit. Army lef·ten′·ənt) noun
1. An officer who fills the place of a superior in the latter's absence or acts for him under his direction; deputy.
2. In the U.S. Army, Air Force, and Marine Corps, a commissioned officer holding either of two ranks, first or second lieutenant, the former ranking next below a captain.
3. In the U.S. Navy and Coast Guard, a commissioned officer holding either of two ranks, lieutenant or lieutenant (junior grade), the former ranking next below a lieutenant commander and the latter next above an ensign.
4. A police officer next above a sergeant and below a captain. [<F lieutenant <lieu place + tenant, ppr. of tenir hold]
—lieu·ten′an·cy noun