When you're too much of a fiend; when you're such a fiend that you can only be defined as a fiendhead.
Ex. Byron's smokes so much that he became a fiendhead.
I think the biggest fiendhead that I know is Tommy.
JUULs aren't CUUL, they only produce fiendheads!
When your so god damn too fucking bored you end up breaking Urban dictionary and end up getting this on your screen.
Guy 1: I just got this message on my screen when typing qeqtyhreuyvyasujicdfvdsucaijxoscndbvhsnciamxc smcdkmvemkv cmsdfk vfb vbndfdnfbndfkmbkdmkdfgkmbgkdmfgkdmgkdmkgmfa,sfsf,sofodg,sof,sfoofofofd *whatever.* it says: Bad Message 431 reason: Request Header Fields Too Large Guy 2: oh... you're so bored you broke it!