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1.
A girl with no booty where her pants can barely stay on without the assistance of a belt.
The kind of bonytail that you don't bounching on your cock because it will be like fucking a wall
by KBCA February 08, 2007
 
2.
A ponytail on a balding man. It can be viewed as a bad cross pollination between an ultimullet and a skullet. Very popular hairstyle in the 1980's.

Also, it is a species of endangered fish (Gila elegans). It is a rare minnow found in the Colorado River.

My bald old man has a bonytail down to his fatass.
by The 80's rock! June 09, 2006