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1.
Face Down, Ass Up: A submissive sexual position in which the female is on her knees, puts her face all the way to the bed or floor, and sometimes reaches back with both hands to spread either side of her vagina or anus.
"I had that bitch FDAU, wearing it out from behind"
by TheOak39 July 15, 2008
 
2.
Face Down Ass Up
A provocative pose where a woman is on her knees with her face to the ground (pillow, etc) and her ass in the air.

The model Lauren Gentile specializes in FDAU poses.
"Lordy, Lauren- that is your sexiest FDAU pose yet..."

"My girlfriend likes it FDAU" (sexual)
by vaughn(psadna) March 30, 2011
 
3.
FDAU stands for Face Down Ass Up
Frat Dude: So what university did she go to?
Frat Dude2: F.D.A.U.
Frat Dude: What's that?
Frat Dude2: Face Down Ass Up!
by Gink September 22, 2006