When your penis slips out of a vagina and the girl comes back down on the penis and folds your boner in half.
Man, my girl was riding me hard last night but all the fun ending quickly when she came down and gave me a bone folder.
by jaided October 22, 2010
A torture device in which someones extremity is placed in order to fold bones at 4 to 6 inch increments until the extremity is destroyed.
(n.)That dickhead should have his arm put in the bonefolder machine.
by Dan Carsley February 04, 2009