A projection, usually on the outside of a building and across from a major point of stress. Source: Julia Ehresmann, "The Pocket Dictionary of Art Terms" <br><br>A mass of masonry or brickwork used as a support or brace counteracting the outward (lateral) thrust of an arch or vault. A pier buttress is a solid mass of masonry. A flying buttress is one which reaches over a side aisle to support the heavy stone roof of a cathedral.Example: Villard de Honnecourt (French, Picardy, 13th century), Reims Choir Buttresses, c. 1230-1635, pen and ink over leadpoint and stylus with occasional additions in bistre wash on parchment, c. 240 x 160 mm. This is the verso of the thity-second leaf in a portfolio of 33 leaves, Bibliotheque Nationale, Paris.Also see aisle, architecture, clerestory, crocket, Gothic, Middle Ages, nave, trabeation, triforium, and vault.