“ CUSP (Lat. cuspis, a spear, point) , a projecting point, or pointed end. In architecture (Fr. feuille, Ital. cuspide, Ger. Knöpfe) , a cusp is the point where the foliations of tracery intersect. The earliest example of a plain cusp is probably that at Pythagoras school, at Cambridge,—of an ornamented cusp at Ely cathedral, where a small roll, with a rosette at the end, is formed at the termination of a cusp. ”