A quick search on "skypunk" gets us an informal description: "Worlds full of floating fortresses, sky battles in agile, obscure fighter planes, or common people shlepping about on islands in the sky." It also gets us the Wikipedia article "Ska Punk", which is quite different and not just somebody saying it with a Southern drawl. Although it does seem that punk music is much more clearly defined than the various "*punk" fiction genres like plumberpunk (which seems to involve little guys with '70s style pornstaches jumping into pipes along with lots of killing and theft).