Definitions
1.NounA dish of glass or earthenware, with a lid, in which food is baked and sometimes served.
2.NounFood, such as a stew, cooked in such a dish."a chicken casserole"
3.NounAny type of food that fills the high-walled dish or pan in which it was cooked. (Can we add an example for this sense?)
4.VerbTo cook like, or as, a casserole; to stew.