Generic product name (albeit a Sony trademark) for very large electronic visual displays. They are most commonly used at stadium sporting events for scoreboards, animations, instant replays and the occasional marriage proposal. JumboTrons have evoled from crude low-resolution monochrome monitors to television-quality displays. The one at the Toronto Skydome cost $17 million.
Sources:
http://www.bigbeefandbeer.com/jumbotronFAQ.htm
http://www.sel.sony.com/SEL/legal/copyrights.html