vault 1 
(vôlt)
(vôlt)n.
1.
a. An arched structure, usually of masonry or concrete, serving to cover a space.
b. An arched overhead covering, such as the sky, that resembles the architectural structure in form.
2. A room or space, such as a cellar or storeroom, with an arched ceiling, especially when underground.
3. A room or compartment, often built of steel, for the safekeeping of valuables: a bank vault.
4. A burial chamber, especially when underground.
5. Anatomy An arched part of the body, especially the top part of the skull.
tr.v. vault·ed, vault·ing, vaults
1. To construct or supply with an arched ceiling; cover with a vault.
2. To build or make in the shape of a vault; arch.
[Middle English vaute, from Old French, from Vulgar Latin *volvita, volta, from feminine of *volvitus, arched, alteration of Latin volūtus, past participle of volvere, to roll; see wel-2 in the Appendix of Indo-European roots.]
vault1top to bottom: barrel, groin, and rib vaults