When a girl has no ass.
My sister.
Damn Pablo, have you noticed that my sister is flatassed!
like fatass, but with super flat people
person a: which person in here haz the biggest boobs
person b: me ofc
person c: no fuck u ur flat af
person a: stfu flatass
Mike Pulaski is a single flatass fatass who keeps eating brisket after brisket. He's gonna be over 300 lbs soon.