butte An isolated hill with steep sides and a small flat top, smaller than mesas and plateaus. Buttes are formed by erosion when a cap of hard rock, usually of volcanic origin, covers a layer of softer rock that is easily worn away. This hard rock avoids erosion while the rock around it wears down. FTT:376 SWEETRealm:Butte TGN:21443 plateau Geonames:T.BUTE https://en.wikipedia.org/wiki/Butte flattened elevation