Basically, you take two food items, merge them together into a cacophony of unnatural proportions, and then eat.
This article documents just some of them, and I've actually tried something called the McGangBang. That is it's actual name and here's a picture of it.
I really feel embarrassed, particularly in light of the good healthy food threads in QK and I've sort of dragged it down to greasy stuff again.
What food combinations do you enjoy eating? What things seem like they shouldn't go together, but...they just do?