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1.
A fat slut; an obese woman who is loose; a fat chick who puts out a lot.
She's such a fattress; her chunky ass had sex with a dozen different guys last semester.
by PMax January 30, 2009
 
2.
A mattress for heavy people
Do you want to swing by Mattress King and pick up a fattress?

She doesn't use a fattress but she's no lightweight either.
by Uncle Fatty June 22, 2008
 
3.
An extra-large bed or gurney used in a hospital for morbidly obese individuals
- Did you see that fatso come in with anasarca?
- Yeah, she was so big her pannus was hanging off her fattress... the dumb bitch.
by Madmanskin July 22, 2010