A complicated idiom used by small, loser-ish people to describe something with great enthusiasm, can be used both positively or negatively. Used in place of words such as motherfucking, or m'f (em effing)
Me: STOP! You're getting on my nerves!

Loser Girl: Ugh! you're so muh'fuh'effing annoying!

Me: Who the fuck says that?!

Loser Girl: Whatever! *farts* and runs away
by IKnoAStarWhenIHearOne January 18, 2013
Get the muh'fuh'effing mug.