a Bishop (or Archbishop) in the Catholic Church, referring to the characteristic headgear they wear (aka the miter), and possibly also to definition #1 as an important characteristic for conehead. Honestly, the first time I heard this definition of conehead was from a Catholic Priest.
1. Referring to one who deepthroats a dick down to its base with the greatest of ease and sense of determination.
2. An individual that partakes frequently and/or often in a fellatious manner.
"The bitch sucked the dick so long and so often I had no choice but to called her Conehead."
"It was insane Bro. She bottomed my shit out every time. She will now go by Conehead as far as I'm concerned."