A secondary floor, in between the main floors of a building; entresol.
On our way to the top floor, we stopped at the mezzanine.
A small window used to light such a secondary floor.
The lowest balcony in an auditorium.
Additional flooring laid over a floor to bring it up to some height or level.
A floor under the stage, from which contrivances such as traps are worked.
Fulfilling an intermediate or secondary function.
To make interconnections easier, we added a mezzanine PCB.