fcn
probably the shortest abbreviation of the formal word 'fucking' or often used 'fucken'
duuuuuuuuuuuuuuuude! that is so fcn epic man :OOOO
FCN
F meaning Fuck, C meaning Cunt, N meaning Nigger
"the three most commonly used negative words consist of FUCK, CUNT, and WE DO NOT (pause) joke about the N word." i.e. FCN