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1 definition by Elphaba. W. Witch

 
1.
Someone who has a flatback as a result of laying on their back too much. Who are of a promiscious nature. Or simply, a female who is a sloppy, loose, trollup.
"man, that Deanna, she is such a flat back, I have seen her with 3 different guys this week!"

or

"Wow, why is he dating that flatback whore?"
by Elphaba. W. Witch July 12, 2008
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