mezzanine

An intermediate floor or storey in between the main floors of a building; specifically, one that is directly above the ground floor which does not extend over the whole floorspace of the building, and so resembles a large balcony overlookin

On our way to the top floor, we stopped at the mezzanine.

[W]ater closet on mezzanine provided with opaque singlepane oblong window, tipup seat, bracket lamp, brass tierod brace, armrests, footstool and artistic oleograph on inner face of door: […]

An apartment, room, etc., on such an intermediate floor.

The lowest balcony in an auditorium, cinema, theatre, etc.; the dress circle.

Additional flooring laid over a floor to bring it up to some height or level.

In full mezzanine window: a small window at the height of a mezzanine floor (sense 1.1) or an attic, used to light these floors.

Characteristic of or relating to high-interest loans which have no collateral, and are regarded as intermediate in nature, ranking above equity but below secured loans.

This new vehicle funded the purchases of these tranches by issuing fixed-income interests to investors who were seeking high returns and who were willing to believe that by repackaging mezzanine tranches in MBS structures, some tranches could be designated as safe enough to obtain a AAA or AA rating.

Fulfilling an intermediate or secondary function.

To make interconnections easier, we added a mezzanine PCB.

To fit (a building or other place) with a mezzanine floor.