A Buddy Boner is an erection that a man gets while hanging out with his male friends. It doesn't mean that he's gay; it just means that he's having a good time.
When Bill and Mark played poker together they each developed buddy boners. Man, were they ever having a good time.
In essence, the same as a "fuck buddy" or "friend with benefits".
I think we can all agree that the alliteration in "bonebuddy" creates a far nicer ring than the two aforementioned examples, and thus it should become the commonly used term.
Blair's bonebuddy is out of town, so he will keep you company tonight.
A considerate dude who frequently/diligently tidies/smoothes/re-adjusts the blankets/pillows while canoodling in bed with you, just as the well-known feathered grass-walled-nest dweller does to please a female who drops in to visit.
Tiffany always appreciates my being a bower-birdbed-buddy, since it feels so much more pleasant to sleep with me if the blankets are always neat and uniformly covering us, especially during the cooler seasons.
Ruler of Lake Titicaca. Rumored to have a bunghole that gets very angry if it does not receive toilet paper. Cornholio the Great is often seen walking around with his shirt over his head and his hands in the air, chanting songs about his power, and his bunghole.
"I am Cornholio! You do not want to face the wrath of my bunghole, for I need TP!"
Butthead: Shut up, Beavis! (uh huh huh huh)
Beavis: Um, okay. (heh heh heh heh).