lightbox

Short definition from Wiktionary

Noun

1. 1
   A box containing a source of light and a white, translucent cover, used to view photographic transparencies.
2. 2
   A box containing fluorescent tubes or LED technology, used to treat people with seasonal affective disorder (SAD) and circadian rhythm disorders.
3. 3
   A kind of pop-up that is overlaid across a web page while the rest of the content is dimmed.
4. 4
   A backbox.
5. 5
   A device used in phreaking that indicates when a telephone line is in use by means of a light.