It is when you and one of your friends goes up to each side of an old person and hits hips and shoulders at the same time. If it was a successful Kaboshki the old person will be lying there with broken hips and shoulders without the ability to move. You can optionally do it with three persons, where the last person hits the tailbone and spine.
A small piece of information. Derived from the word ken, used often in the scottish language and is synonymous with knowledge.
Person 1: "Hey I don't get this shit. How do you solve this problem?"
Person 2: "I got that one. Give me some kenlets on this assignment and I'll help you w/ that one."