"Supergun" is a term for an adapter intended to allow JAMMA-compatible arcade boards to be used with standard home video equipment. Normally, you'd need an arcade cabinet with a JAMMA port, compatible arcade-RGB display, and all the wiring harnesses behind it, but that is a space hog and most people don't want one in their house.
Fair enough, I guess I'm assuming too much knowledge-- a supergun is just a device designed to take a JAMMA arcade connector and provide everything an arcade cabinet would do for a home setup. (i.e., provide video output, some sort of game controller input, bring audio levels down from amplified JAMMA to line level)
I've talked about playing arcade boards at home on the blog so often I sometimes forget to be more accommodating to new readers.
