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3.
1.to take it the gayest way possible. 2.to be taken advantage of.
The bossman really backdoored me this time.
by Travmanicas March 02, 2007
 
1.
putting some ones penis up ur ass
as in sorority girls, hey that's the girl Jimmy backdoored!
by shoes October 17, 2003
 
2.
To go behind someones back or if someones betrays you.

Also used in Big Brother USA if someone betrays a member of their team
That bitch backdoored me.
You backdoored me man.
by edward banana figures August 18, 2006
 
4.
To hit someone in the back of the head , running or not.
White Guy : *Not paying attention to anything*

Black Guy 1: *Runs at extreme speeds and hits white guy in the back of the head.*

Black Guy 2: "DAMN! He just backdoored the shit outta that white guy!!"
by Hyrohimaru May 31, 2010
 
5.
To go on a night out with the LADs and sneak off home without telling anyone at too early a stage in the evening.
LAD 1: Wait, where's Elliot gone?
...10 minutes later after looking high and low...
LAD 2: What a swiller! He must've backdoored it.
by Hot Chocolate Slut August 25, 2014