de-kegged

Pulling somebodys trousers/shorts/skirt and occasionally also their underwear as a prank.

see for beans for usage of it.

De-Kegging, The removal of the pants and underwear in one swift movement by a third party.

This practice was brought about in British Prisons, Boarding Schools and Borstals around the 1970's, this involves a person sneaking up behind another person (Typically boys) and grabbing their pants waistline.

This is followed by a swift downwards pull taking the victims pants and underwear to their ankles.

Masked as a way to humiliate the person publicly, this is actually a homosexual based act which allows the first person to see the victims penis & size whilst playing the "i did it for a laugh" card, thus covering the first persons intended sexuality.