Backside
Pronunciation : Back"side`
Part of Speech : n.
Etymology : [Back, a. + side. ]
Definition : Defn: The hinder part, posteriors, or rump of a person or animal.
Note: Backside (one word) was formerly used of the rear part or side of any thing or place, but in such senses is now two words.
Source : Webster's Unabridged Dictionary, 1913