Fack 

Slang for the swear word, fuck. Used when there is a strong dislike between two people or things.

Fack you, I facking hate you.

Fack by M-Lap August 2, 2007

Fack 

THE GROSSEST SONG EVERR! eminemis dirty and very discusting. but funny at the very same time

eminem- SHOVE A GERBIL UP MY ASS THROUGH A TUBE!

person watching the video- OMG OMG fack is soooooo funny

Fack by fackisfunny February 8, 2009

fack 

Synonymous with the word 'fuck.' Notably used in cases where the writer does not know (American) English well and in attempt to sound out the word while applying his known letter/pronunciation set results in a slightly mangled but understandable version of the word.

Example at engrish.com, where some silly Japanese bastard decided to spraypaint profanities on the wall yet failed in his (American) English spelling:
Fack You Man

(alternately pronounced as 'fack', similar to the word 'fact', to those who find such objects of Japanese word scrambling humorous and to explicitly specify that you are not saying the word 'fuck', but rather the word 'fack')

fack by Stimar May 7, 2003

FACK 

The FACK algorithm is based on first principles of congestion control and is designed to be used with the proposed TCP SACK options. By decoupling congestion control from other algorithms such as data recovery, it attains more precise control over the data flow in the network.

"FACK my network, please"

FACK by Serafim February 9, 2007

Fack 

When you hit someone in the belly

Oohhhhh, you just facked me!

Fack by Patria o Muerte April 23, 2022

fack 

To be confused; baffled

"What the fack?"

fack by Andrew December 28, 2003

fack 

A prolonged way of saying "fuck" when you are busted in an awkward/uncomfortable situation.

Timmy: "Chaz shit his pants yesterday."

Shelly: "He's sitting right behind you..."

Timmy: "Fack..."

fack by Mere Scraps August 2, 2009