barrel vault(n = noun.artifact) - the simplest form of vault; a single continuous arch;
is a kind of vault

bank vault, barrel, barrel cactus, barrel knot, barrel maker, barrel organ, barrel process, barrel roll, beer barrel, burial vault, golden barrel cactus, groined vault, gun barrel, pickle barrel, pole vault, pork barrel, rain barrel, rear of barrel, ribbed vault, trash barrel, vault, vault of heaven, wine barrel