The Collaborative International Dictionary of English v.0.48:
Rear \Rear\, a.
Being behind, or in the hindmost part; hindmost; as, the rear
rank of a company.
Rear admiral, an officer in the navy, next in rank below a
vice admiral and above a commodore. See Admiral.
Rear front (Mil.), the rear rank of a body of troops when
faced about and standing in that position.
Rear guard (Mil.), the division of an army that marches in
the rear of the main body to protect it; -- used also
Rear line (Mil.), the line in the rear of an army.
Rear rank (Mil.), the rank or line of a body of troops
which is in the rear, or last in order.
Rear sight (Firearms), the sight nearest the breech.
To bring up the rear, to come last or behind.