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2.
The apple shaped, bell bottom, part of your ass that hangs out the side of a thong.
Ey Fatty, you got a nice fatty batty.
by No middle name fatty. October 21, 2009
 
1.
Refers to the rear end of a person (usually a women) with a very fat wobbly arse.
"You have a very fatty batty ses I!"

"LOOK AT THAT FATTY BATTY"
by Jason Winder May 04, 2006