Light-boxes meaning : A box containing a source of light and a white, translucent cover, used to view photographic transparencies. A box containing fluorescent tubes or LED technology, used to treat people with seasonal affective disorder (SAD) and circadian rhythm disorders. A kind of pop-up that is overlaid across a web page while the rest of the content is dimmed. A backbox. A device used in phreaking that indicates when a telephone line is in use by means of a light.