Flying buttress
The flying buttress (arc-boutant, arch buttress) is a specific form of buttress composed of a ramping arch that extends from the upper portion of a wall to a pier of great mass, to convey to the ground the lateral forces that push a wall outwards, which are forces that arise from vaulted ceilings of stone and from wind-loading on roofs. The namesake and defining feature of a flying buttress is that it is not in contact with the wall at ground level, unlike a traditional buttress, and transmits the lateral forces across the span of intervening space between the wall and the pier.