A prank pulled on your friends, where you grab one by the shoulders and forcefully ram your knee into their anus. Patented by the famous Aaron Kirk. One may confuse a kirk-a-jerk with farting while having a penis in your anus.
"I saw kaps doing some kind of bodybuilding bullshit, so i took the opportunity to give him one good kirk-a-jerk. Man did he yelp"
by drewbin arubin April 18, 2006