https://en.wikipedia.org/wiki/Casserole
I think "pie" gives a decent idea of the consistency, though as you said not the ingredients, though even the consistency can vary wildly. I've had everything from hamburger casserole, which really is like what you might imagine if I said "hamburger pie" to you except it's in a casserole dish, to green bean casserole, which is pretty much just green beans and melted cheese and has a much soupier consistency.