A person who holds a position auxiliary to another and assumes some of the superior's responsibilities
"Lieutenant," the uniformed officer said to him, "This guy has information on the victim."
After a series of clicks, the lieutenant barked into the phone.
He just came in now, Lieutenant Anderson.
He was at that time serving as a lieutenant in the Prussian life-guards at Potsdam.
The lieutenant never looked the man he was speaking to straight in the face; his eyes continually wandered from one object to another.