https://www.chicagotribune.com/g00/dining/chi-defining-wisconsins-supper-club-culture-20150119-story.html?i10c.ua=1&i10c.encReferrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8%3d&i10c.dv=2
i think this article sums it up "i know it when i see it".
basically a place you go on Saturday night for prime rib & whiskey old fashioned's. almost always preceded by an hour wait in the ante-room/bar where you shoot the breeze with people you know who also happen to be there.
you sit at a table with white linen. there's probably a rustic or outdoorsy decor. there's a plate of celery/cauliflower/carrot/olive at your table when you sit down. you have no choice in this matter. you get a cup of coup and a salad. then your prime rib comes out an hour later with a baked potato. always a baked potato. you can ask for something else but they might kick you out. you can get something other than prime rib.. fish.. a steak. nothing fancy. just a big ####### pile of whatever meat you choose. there's are no 6oz. filets here. if you order prime rib, it's 32oz. if you get a steak, it's 40oz. if you want fish.. it's enough to feed 3 people.
the whole meal costs $22.95 and you will be in a full on drunken meat sweat before you're done.
it's as quintessentially a Wisconsin experience as eating cheese, drinking milk and being a fan of the Packers.