Also called proscenium arch.the arch that separates a stage from the auditorium. Abbreviation:pros.
2.
(formerly) the apron or, esp. in ancient theater, the stage itself.
Origin: 1600–10; < L proscēnium, proscaenium < Gk prosknion entrance to a tent, porch, stage (LGk: stage curtain), equiv. to pro-pro-2+ skēn() (see scene) + -ion neut. n. suffix
1606, "stage of an ancient theater," from L. proscaenium, from Gk. proskenion "the space in front of the scenery," also "entrance of a tent," from pro "in front" + skene "stage, tent, booth." Modern sense of "space between the curtain and the orchestra" is attested from 1807.
[proh-see-nee-uh
m, pruh-] 
nion