Top definition
The act of masturbation while resting your chin on a windows seal and watching your neighbor lay out in the sun. All the while, dressed in nothing but a 1985 pair of terry cloth running shorts cut so short that simply sitting on the bed exposes a hint of your grundel and nut bag.
"Man, my mom caught my brother window jacking the other day. He must have been mesmerized by her bikini spider."

"Dude that's tore."

"Yeah, he couldn't put it away fast enough because he was giving himself the shocker at the same time."
by liquidnails May 02, 2006
Get the mug
Get a window jack mug for your buddy Rihanna.