The act of multiple men sodomising eachother in a human train. Just before ejaculating each one pulls out and blows their load all over the back of the guy in front shouting "twenty-one !"
Damien the sick fuck went out and played backjack with 5 guys he met at a gay bar.
To extricate ones testicles onto the back of ones partner. In other words to withdraw and jack onto your partners back.
Onanism, Ice The Cake, Paint the Lady.
At the last minute she told me she wasn't on the pill so I had to back jack her.
I was going to blast insider her but she is his mum so I back jacked it.
the act of paying someone back in cigarettes for a cigarette bummed earlier.
catherine: hey john, can i bum a cigarette?
john: sure, as long as you backjack me
A form of masturbation where you slide your hand down your dick with your hand backwards, forefinger and thumb touching eachother. Your thumb should be facing in twards your balls and your pinky out twards the head.
Painting a face on your hand is optional.
"Sometimes I rub one out backjack style to shake things up a bit."
the art of bending the penis through the back of the legs for a handjob
she said she was gonna show me something ive never seen before so she pulled my pp through my legs and gave me a backjack