What is Fumf?
1.
short for f#!k you mother f*^$&r
'Man you suck'
'fumf, ill beat your ass'
2.
fumf - fucked up motherfucker
Usually used if we are describing someone crazy or out of their mind.
John: Hey man! Did you see James?! He was driving 150 MPH on this short, narrow street!
Jerry: Yeah. He really is a fumf.
See