It is a very good pranks and makes the victim smell your dirty farts.
This prank was origanally made from a Ukrainian prankster and it is like a gas mask when you put it on there face therefore it is name "Ukrainian Gasmask"
Slangs for this term include "The Dirty Ukrainian" and "Sour Cabbage Surprise"
Billybob: OWTF!?!?! that smells like shit!!!
Matt: Rofl lol!!!