| a vault composed of a number of concave conoidal surfaces, usually four, springing from the corners of the vaulting compartment and touching or intersecting at the top, often decorated with ribs. |
| fan vault n. A vault in which curving ribs radiate upward like the ribs of a fan to form concave half cones that meet or nearly meet at the apex. Common in late English Gothic architecture, fan vaults are often decorated with intricate tracery or paneling. |