When someone is bothering you, on purpose, and won't leave you alone when you are trying to get something done, they are assturbing you. As in, they are disturbing you, and being an ass about it.
In an wordFPS game, killing an enemy player from behind, often after some following. Since the enemy does not know about the threat and thus becames an easy prey. Considered as lame behavior.
Your in a bathroom stall, but instead of shitting in the toilet you shit on the floor, ceiling, and walls, and end up puking in the toilet but missing.
Pretty much, you get your shit all over the fucking place. And not the fucking place it should be.