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1.
The best type of girl.
All good girls take it up the arse. If she's not a backdoor betty she's no lady.
by The big G March 23, 2004
 
2.
A woman who likes to take it in the ass.
Mike's girlfriend is a back door betty.
by TAC April 28, 2003
 
3.
A slut who takes it in the poop chute often!
damn that backdoor Betty sure loves it in the arse!
by opotimus April 03, 2006
 
4.
A girl that enjoys anal sex, sometimes even over vaginal sex. This is usually a secret preference, and not advertised by the girl, to avoid jokes and to protect her "reputation" as a "nice" girl.
She'll never admit it, but I've heard that she's a Backdoor Betty!
by TheMaskedMarvel January 31, 2010