A word that just rolls out of your mouth when you're extremly pissed and try calling someone a cocksucker but by the
time you're half-way into the word your anger has escalated so much that all you wanna say is 'fuck'.
Also can happen if you've been using 'fuck' so many times that your
brain doesn't have the
time to override 'fuck' with the next syllable of the word you're trying to say.