Voussoirs forming a stable arch; there are special terms for the voussoirs at the base of the arch and for the (usually single) voussoir at the top centre
 Borrowing from French voussoir, from Old French vosoir, from Vulgar Latin *volsorium, from *volsus, from Latin volvō (“I roll”).
voussoir (plural voussoirs)
- (architecture) One of a series of wedge-shaped bricks or stones forming an arch or vault.
wedge-shaped brick or stone