A pejorative term used mostly in fight scenes. It is likely a variant of butthole. Coined by Gary Busey's character Frank McBain in the Cold War thriller 'Bulletproof'.
"Your worst nightmare, butthorn!"
"Bird season is over, butthorn!"
Bored I could have sworn I saw this episode of "I'm With Busey"
StanleyPain I dare say those men did not understand the warden's contention that it was definitely not bird season, so he had no choice to emphasize his point.
sosage You guys are due on the Commando set...butthorn.