part — a portion or division of a whole that is separate or distinct; piece, fragment, fraction, or section; constituent: the rear part of the house; to glue the two parts together.
rear — the back of something, as distinguished from the front: The porch is at the rear of the house.
rudder — Nautical. a vertical blade at the stern of a vessel that can be turned horizontally to change the vessel's direction when in motion.
appendage — An appendage is something that is joined to or connected with something larger or more important.
behind — If something is behind a thing or person, it is on the other side of them from you, or nearer their back rather than their front.
buttocks — the two large fleshy masses of thick muscular tissue that form the human rump
conclusion — When you come to a conclusion, you decide that something is true after you have thought about it carefully and have considered all the relevant facts.
posterior — situated behind or at the rear of; hinder (opposed to anterior).
reverse — opposite or contrary in position, direction, order, or character: an impression reverse to what was intended; in reverse sequence.
rump — the hind part of the body of an animal, as the hindquarters of a quadruped or sacral region of a bird.