look up any word, like usuratonkachi:
 
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
 
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