the back part of something, e.g.:
the part of something located opposite its front
the rear of a house
the part, e.g. of an army, that is furthest from the enemy
informal the buttocks
the space or position at the back
He moved to the rear
bring up the rear
to be the last in a group, series, order, etc
[Middle English via Old French rere from Latin retro: see retro-]