A "dance marathon" is an event where people dance for a long period, usually hours or even days, to raise money for a cause. It's like a dance party, but it might continue for a much longer time. Full definition
He has conducted dance marathons in Palestine; Karaoke performances of the Strokes songs in Bogota, Istanbul, Jakarta, and Bunbury; hoax Hollywood screen tests in war - stricken Baghdad — and has even dabbled with reality TV in Iraq, Turkey, and Britain. (brooklynrail.org)
for the impetus of the charity dance marathon craze that began on many campuses back then. (sbnation.com)
After all, he reasoned, hadn't dance marathons proved immensely popular? (si.com)