Bushing the firing pin hole is where it is drilled out and a tube or bushing is threaded into the hole. The inner diameter of the bushing is then drilled for a precise match to your firing pin. This results in better support for the primer cup and no place for the cup material to flow into. Google it and I bet you can find photos or even tutorials.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli