from
The Collaborative International Dictionary of English v.0.48
Mezzanine \Mez"za*nine\, n. [F. mezzanine, It. mezzanino, fr.
mezzano middle, fr. mezzo middle, half. See {Mezzo}.]
1. (Arch.)
(a) Same as {Entresol}.
(b) 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.
[1913 Webster]
2. A flooring laid over a floor to bring it up to some height
or level.
[Webster 1913 Suppl.]
3. Also
{mezzanine floor}. (Theat.) A floor under the stage, from
which various contrivances, as traps, are worked.
[Webster 1913 Suppl.]
4. The lowest balcony in a theater, or the forward part of
the first balcony.
[PJC]