Tavern sandwich
A tavern sandwich (also called a loose meat sandwich or loosemeat) is a sandwich consisting of ground beef on a bun, sometimes mixed with sauteed onions, and sometimes topped with pickles, ketchup, mustard, raw onions, and/or cheese.
Unlike a hamburger, a tavern's meat is cooked loose rather than formed into a compact patty. It more closely resembles a sloppy joe, without the tomato-based sauce.