coulisse

[koo-lees] /kuˈlis/
noun
1.
a timber or the like having a groove for guiding a sliding panel.
2.
Theater.
  1. the space between two wing flats, leg drops, or the like.
  2. any space or area backstage.
  3. wing flat.
Origin
1810-20; < French: groove, something that slides in a groove; see portcullis
British Dictionary definitions for coulisse

coulisse

/kuːˈliːs/
noun
1.
Also called cullis. a timber member grooved to take a sliding panel, such as a sluicegate, portcullis, or stage flat
2.
  1. a flat piece of scenery situated in the wings of a theatre; wing flat
  2. a space between wing flats
3.
part of the Paris Bourse where unofficial securities are traded Compare parquet (sense 4)
Word Origin
C19: from French: groove, from Old French couleïceportcullis