Vault light

Vault \Vault\ (v[add]lt; see Note, below), n. [OE. voute, OF.
   voute, volte, F. vo[^u]te, LL. volta, for voluta, volutio,
   fr. L. volvere, volutum, to roll, to turn about. See
   {Voluble}, and cf. {Vault} a leap, {Volt} a turn, {Volute}.]
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   1. (Arch.) An arched structure of masonry, forming a ceiling
      or canopy.
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            The long-drawn aisle and fretted vault. --Gray.
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   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." --Milton.
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            The silent vaults of death.           --Sandys.
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            To banish rats that haunt our vault.  --Swift.
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   3. The canopy of heaven; the sky.
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            That heaven's vault should crack.     --Shak.
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   4. [F. volte, It. volta, originally, a turn, and the same
      word as volta an arch. See the Etymology above.] A leap or
      bound. Specifically:
      (a) (Man.) The bound or leap of a horse; a curvet.
      (b) A leap by aid of the hands, or of a pole, springboard,
          or the like.
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   Note: The l in this word was formerly often suppressed in
         pronunciation.
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   {Barrel vault}, {Cradle vault}, {Cylindrical vault}, or
   {Wagon vault} (Arch.), a kind of vault having two parallel
      abutments, and the same section or profile at all points.
      It may be rampant, as over a staircase (see {Rampant
      vault}, under {Rampant}), or curved in plan, as around the
      apse of a church.

   {Coved vault}. (Arch.) See under 1st {Cove}, v. t.

   {Groined vault} (Arch.), a vault having groins, that is, one
      in which different cylindrical surfaces intersect one
      another, as distinguished from a barrel, or wagon, vault.
      

   {Rampant vault}. (Arch.) See under {Rampant}.

   {Ribbed vault} (Arch.), a vault differing from others in
      having solid ribs which bear the weight of the vaulted
      surface. True Gothic vaults are of this character.

   {Vault light}, a partly glazed plate inserted in a pavement
      or ceiling to admit light to a vault below.
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