Mezzanine

n.
  1. (Arch.) A floor under the stage, from which various contrivances, as traps, are worked.
  2. The lowest balcony in a theater, or the forward part of the first balcony.
    1. Same as Entresol.
    2. A partial story which is not on the same level with the story of the main part of the edifice, as of a back building, where the floors are on a level with landings of the staircase of the main house.