Those rolls of ground beef wrapped in plastic. They're usually packaged off-site and may come frozen. They look like a huge sausage. Think Jimmy Dean sausage, but with GB. I think that was what Vit was referring to. I buy my GB on the styrofoam tray covered in plastic wrap that they grind at the store.
I call them chubs, too. And sometimes a hunk of bologna, like what I've shown smoking before, is referred to as a chub by BBQers. I'm not really sure when the term transferred to certain meats.