1.(Arch.) An arched structure of masonry, forming a ceiling or canopy. "The long-drawn aisle and fretted vault."
2.An arched apartment; especially, a subterranean room, used for storing articles, for a prison, for interment, or the like; a cell; a cellar. "Charnel vaults." "The silent vaults of death." "To banish rats that haunt our vault."
3.The canopy of heaven; the sky. "That heaven's vault should crack."