The term 'cafeteria staple' refers to food items that are commonly found in school cafeterias. The crossword solutions for this term are 'TRAY' (4 letters) and 'mysterymeat' (11 letters). A TRAY is a flat, shallow container with a raised edge that is used to carry food items. Mysterymeat is a type of processed meat product that is often served in school cafeterias. It is usually made from a combination of different meats and is not identified by its source.