This is "
f u c k" spelled backwards. It is used to convey the emotion and intensity of the word "
f u c k" without actually using it.
Mostly used when one does not want to physically SOUND vulgar, or offensive (even though they intend to).
Used on websites such as YouTube, which
block offensive words
Kcuf man, these
guys can
dance!
Kcufing hell, get a permit before you
post a video.
John: Ha ha, you didn't wipe your ass
Smith: Kcuf off!