when more than 3 guys make an anal sex train. grinding in and out of each other's anus like a locomotive. the guy in front is called the conductor.. all partneers thereafter are called cabooses.
"dude, i was at that gay club the menagerie the other night and these 5 guys were having a wicked crazybone train."
One who is of little intelligence and/or someone who acts in an unpleasant manner, a derogatory term as to compare someone to a penis inside of a brain.
I was building a giant horse dick in Minecraft and he blew it up with TNT, what a Bonerbrain!
The act of performing "spirit fingers" in front of your crotch while exclaiming "BONER FINGAHS!" can be used as a method of saying hello, or describing something as awesome.
Person a: oh bonerfingers.
Person b: whats up man.