casserole pronunciation [kas-uh-rohl] noun, verb, -roled, -rol·ing.
1. a baking dish of glass, pottery, etc., usually with a cover.
2. any food, usually a mixture, cooked in such a dish.
3. a small dish with a handle, used in chemical laboratories.
That last one came as a surprise to me.
More relevant to those of us who cook:
A casserole refers to both a baking dish and the ingredients it contains. Casserole cookery is extremely convenient because the ingredients are cooked and served in the same dish. A "casserole dish" usually refers to a deep, round, ovenproof container with handles and a tight-fitting lid. It can be glass, metal, ceramic or any other heatproof material. A casserole's ingredients can include meat, vegetables, beans, rice and anything else that might seem appropriate. Often a topping such as cheese or bread crumbs is added for texture and flavor.