Although "ball and chain" is usually used to humorously refer to ones Significant Other, it can also be used to mean any other sort of yoke (physical or otherwise) that holds one back. Originally the "ball and chain" referred to the heavy iron ball that was attached to a prisoner's leg to hobble him.

In Nethack, you are stuck with a ball and chain if you read a cursed or uncursed Scroll of Punishment. The ball and chain is not completely useless, though, you can pick it up and use it as a weapon (albeit a very poor one), or if you polymorph into a rust monster you can eat it for sustenance.