Freebase(0.00 / 0 votes)Rate this definition: A casserole, from the French word for saucepan, is a large, deep dish used both in the oven and as a serving vessel. The word casserole is also used for the food cooked and served in such a vessel, with the cookware itself called a casserole dish or casserole pan. In British English, this type of dish is frequently also called a bake, coinciding with the cooking technique used to cook casseroles.