Low quality food that looks stale and unappetizing but costs relatively cheap. Usually is tax-free. Depending on your school, there will be days where the cafeteria serves higher quality food, such as Taco Bowl Tuesdays.
Only to be eaten when your mom didn't pack you lunch, or when you're too lazy or busy to walk to the nearest food place.
My mom forgot to pack my lunch so I went to order some cafeteria food. Unfortunately all the good stuff had been sold out and was left to order one of those sad-looking dried out cheeseburgers.