This is one of those hilarious pranks that frat boys are always playing on each other. By "hilarious," of course, I mean "somewhat pervy, and pretty annoying." It's a small bomb that, when thrown, produces a localized magical field that causes people's pants to fall off. They can pull them back up, of course, but it's too late. You've seen everything.
Oddly enough, the spell is so strong that it causes people's pants to fall off even if they're not wearing pants, and even if they don't even have legs. Weird, man.
Type: combat item
Selling Price: 130 Meat.
(In-game plural: depantsing bombs)