look up any word, like sparkle pony:
 
1.
Fat chick, no boobs.
Size 22 chick, "A"cup is a flatso.
by Galicia December 08, 2006
 
2.
A fat girl with small tits
That flatso looks like my uncle Joe with long hair!
by Michael Hunt August 06, 2003
 
3.
(N.) An Overweight Adult Female who's a Member of the "Itty Bitty Titty Committee." Usually UGLY and SMELLY, these broads are the worst (and usually fattest) of the Bertha Bovine family.
Mrs. Hunt is a Flatso.
by G-Union 2 November 10, 2004