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1.
Noun - Power panties used by portly people for the illusion of slimness. Also, exclamation - shorthand for saying "Thanks!"
"I ate too much prime rib at the buffet and can only fit in my Jordache jeans with the help of 'ma Spanx!" Also, "Spanx for the memories..."
by Dawn Bolter February 10, 2005
 
2.
meaning special thanks, thank you with more gratitude
spanx for the gift
by Donald W. Brown Jr March 12, 2011