What is "cloister vault"

n. (context architecture English) A vault resulting from the intersection of two barrel-vaults crossing in a right angle. The angles of intersection are groins with projecting angles at the base, which die away at the summit.

In architecture, a cloister vault or domical vault is a vault with four concave surfaces (patches of cylinders) meeting at a point above the center of the vault.

It can be thought of as formed by two barrel vaults that cross at right angles to each other: the open space within the vault is the intersection of the space within the two barrel vaults, and the solid material that surrounds the vault is the union of the solid material surrounding the two barrel vaults. In this way it differs from a groin vault, which is also formed from two barrel vaults but in the opposite way: in a groin vault, the space is the union of the spaces of two barrel vaults, and the solid material is the intersection.