spandrel, n. Archit.
1 the almost triangular space between one side of the outer curve of an arch, a wall, and the ceiling or framework.
2 the space between the shoulders of adjoining arches and the ceiling or moulding above.
spandrel wall a wall built on the curve of an arch, filling in the spandrel.
perh. f. AF spaund(e)re, or f. espaundre EXPAND