The act of jacking off your boyfriend whist he is sat behind you as you are typing this onto his laptop at the same time. During this he is sitting on his Nintendo DS playing Pokemon.
Example: having a laptop on your knee; sitting on the end of the bed; penis in hand! There you have, a backjack!
by Carrots. June 29, 2014
The act of traveling across country, sperm bank to sperm bank, funding your travels with your ejaculate
by Nero1313 October 2, 2015
Performing the ol' reach around on yourself, an advanced masturbation technique. Word origins can be traced to dudefuckinghellyeah (DFHY) at burning man 2009.
The stranger is getting old, I think today I'll change things up and pull a dactyl backjack when I'm wanking.
by 1009 September 20, 2009
During Sexual Intercourse, A woman sticks her one of her tits into the mans asshole, and reaches around and jacks you off at the same time.
by Dillon Coolman June 13, 2011
When a woman sticks one of her tits in the mans ass hole and reaches around and jacks you off from behind.
by D-speed June 13, 2011