Voussoir

Part of speech: noun

Pronunciation: /vuˈswɑːr/

Definitions

1. a wedge-shaped stone or brick that forms part of an arch or vault in architecture
2. one of the tapered blocks arranged in a circular pattern to create an arched structural element
3. a radiating stone unit positioned within an arch that distributes weight downward and outward

Etymology: The arch stones that form a curved vault or arch are wedge-shaped because of a Latin verb meaning "to roll." The French term "voussoir" descends from Old French "vosoir," which came from a Vulgar Latin form "volsorium," built on "volsus," the past participle of "volvere." The idea behind it is the turning or rolling of the arch: each stone is cut so that it pivots into place against its neighbours, and the whole curve is held up by the pressure between them. English took the word directly from French without adapting its spelling, so it still looks and sounds French. Its use in English is largely confined to architecture and stonemasonry, where the wedge-shaped stones of an arch are described by the term. The keystone, the central stone at the top, is the one special case among them.