(n): any part of an organism such as an organ or extremity
(n): a tooth situated at the back of the mouth
(n): hard bonelike structures in the jaws of vertebrates; used for biting and chewing or for attack and defense
(adj): vs. anterior) -- (located at or near or behind a part or near the end of a structure
(adj): prenominal), hind(prenominal), hinder(prenominal) -- (located at or near the back of an animal
(adj): situated in or directed toward the part of the body from which the tail arises
(adj): at or near or toward the posterior
(adj): prenominal), ulterior, posterior -- (coming at a subsequent time or stage
(adj): vs. antecedent) -- (following in time or order
How about fundament?
This might be the most dignified word for 'ass' I can think of.