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1.
someone who gives it up too fast or is easy
that girl is a fast ass
by anynomus person hahaha August 22, 2007
 
2.
It means precocious. It does not necessarily mean whore or easy, as defined in the previous definition. It particularly applies to young girls
Oh, that child is just too grown. she is a (fast ass) little thing
by Ms M August 08, 2013
 
3.
Term for men, of any sexual preference, who fuck to fast

Or indeed it could be used for a lady, wearing a strap-on and going for it in a fast manor.
"I walked into the room and saw Gary's fast ass pounding away on that fat chick from Friday night"
by djsaltynuts October 25, 2013