cyclorama

Often abbreviated to "cyc". [As with the word "proscenium, comes from the Greeks.] A large sheet of natural (unbleached) muslin, canvas, leno (filled-scrim) or plastic hanging as far as possible upstage and often used to represent sky. If made from robin's-egg blue-colored material, called a "sky cyc". If the ends wrap downstage, called a "wrap cyc". If made of plaster, called a "plaster cyc". If lit from the rear, must be of a seamless material, at significantly greater cost. A cyc is never painted, so do not confuse it with a "backdrop".