A baseball bat(or any club like object) which has had a hole drilled in the middle and a metal pipe, bar, or metal powder/dust placed inside and the hole sealed shut. The purpose is to increase the weight and rigidity of the weapon.
A sexual performance where the man is engaging in sexual intercourse with a girl through her anus. As she is penetrated fiercefully, she will begin to moan. One the moaning begins, the man simply slams her in the back with a sledge hammer.
One of my personal new favorite sexual fantasies is the back breaker. I love seeing her bones shatter to dust!
When Greg walked into the conference room for the interview he was wearing jean shorts and birkenstocks. The interviewee cringed so hard he heard his back break. Greg's look was a real back breaker.