noun: (film) The filmmaking technique of shooting foreground action against an evenly-lit monochromatic background for the purpose of removing the background from the scene and replacing it with a different image or scene.
noun: (film) The visual effect resulting from this technique as well as the colored screen itself, especially blue.
noun: (computing) Ellipsis of blue screen of death. [(computing, informal) An error screen displayed by some operating systems, especially Microsoft Windows, after encountering an unrecoverable error which causes the system to shut down.]