A butte is a geographical feature. It is a lone hill with steep sides and a top that is generally flat. It differs from a mesa in that it is smaller and narrower.
Some areas that contain well-known examples of buttes with flat tops include Monument Valley in Utah and the Devil's Tower in Wyoming. The rule about buttes having a flat top is not hard and fast, as evidenced by Black Butte in Oregon and Bear Butte in South Dakota. Some formations that are larger than traditional buttes also bear the name, such as Crested Butte in Colorado. Butte is also the name of a Montana city.