Could be a reference to an annoying or self absorbed person who could either be bragging far too much or putting others down in a manner that is unacceptable.
This could also be used as a cuss word for when you may be in trouble, angered at something that has happened at that immediate moment, or are in the process of being completely screwed. This is similar to the meme "FFFUUUU!"
James: Hey, I got an A+ on the test and you got a D. You fail! Haha!
Cory: You buttfuck...
---
Tim: I'm being mauled by the zombies! HEELP!
Michael: I'm at the other side of the map, I can't help you!
Tim: BUUUUTFUUUUUUUCK
Anything That Will Upset Your Butt, and Cause a Case Of Butt-pee.
Man, i just had a buttfuck sandwhich..
If you're seriously looking up "buttfuck" you have serious issues. Pervert....
When the people at gamestop buy your 50$ game for 9$, then they put it right back on the shelf for 49.99$.
Clerk: Hi welcome to gamestop, can I interest you in a buttfucking.
Customer: No thanks, I'll just sell my shit on ebay.
What happens to you when you use AOL.
I signed up for 300 free hours with AOL, and then preceeded to bend over and spread my cheeks...
to ram in the ass with a penis or dildo
dickhead
i want to buttfuck your sister