The arch that forms a frame at the front of a stage.
(Or "pros arch"). The actual opening of a proscenium stage.
Abbrev. to Pros. The archway which separates the stage and the auditorium. 
[n] - the arch over the opening in the proscenium wall
The arch around the front of the stage.
noun the arch over the opening in the proscenium wall
the name derives from the Greek work, skene. Originally skene referred to a building for actors changing at the back of the acting area in a Greek amphitheatre; it therefore implied a version of permanent sc(k)enery. Thus, proscenium denoted a space in front of the back scenery. Proscenium is now taken to mean the front opening of the stage and its...