From Longman Dictionary of Contemporary Englishtelethontel‧e‧thon /ˈteləθɒn $ -θɑːn/ noun [countable] a long television show in which famous people provide entertainment and ask people watching to give money to help people
Examples from the Corpus
telethon• Samit is the leading force behind the Net-A-Thon, an on-line cross between a telethon and a charity silent auction.• It added a special touch to our telethon.• At the same time a reforestation telethon will be broadcast live via satellite and by radio around the world.• A large number of disabled people take part in the Telethon and are grateful for the help they get from the telethon.• It was the last night of the telethon.Origin telethon (1900-2000) television + -thon (as in marathon) 