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The skin or fold that the butt creates when standing up, and dissappers when bending over. Its the space between the upper thigh and the bottom of the booty. Common is girls with large behinds.
DAYUM! that girls ass is so damn big that you could hide a hamster in that booty knuckle!
by Brooke Is a SKANK August 19, 2009

Words related to Booty Knuckle

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