Batty jaw refers to the butt cheeks, arse or buttocks of a person/animal.
Origin from botty (plural botties)
(childish, slang) for bottom.
Clap your batty jaws, them.
You need to wear a better shorts to cover up your batty jaw.
Refers to the cheek of your bum bum.
I fell and landed on my batty jaw. Hurt like hell.