The act of "rubbing one out" without the use of hands. This can be done various different ways. The most popularway is grinding against one's own pants.
Ricky was busy playing guitar, so he used The Amputated Hand trick.
To completely cut off or end an intimate relationship with a guy or girl.
Jeff: "Man, I caught her cheating again tonight. I know she loves me, but still it hurts every time. I don't know what to do."
Jeff's friend: "You know Jeff, I'm sorry about this, but I think we're going to have to amputate. Lock the doors, Marty!"
*Marty locks doors*
Jeff's friend: "You're not seeing her tonight, Jeff, or ever again."