look up any word, like blumpkin:
 
1.
A term used to describe a woman who has a slender back and a narrow waist but has unusally wide hips and out of proportion to the rest of her body.
She's cute but she's got a real banjo butt crammed into those jeans.
by Edword August 01, 2006
 
2.
A flat, puddle, pancake or banjo shaped ass caused by excessive time spent posting online.
That poor fool on my motorcycle forum with 100,000 posts must be a real Banjo Butt.
by Seventy One December 18, 2013