Definition of radiothon in US English:

radiothon

noun

US
  • An especially prolonged radio broadcast, usually as a fund-raising event for a charity or cause.

Origin

1950s; earliest use found in Coschocton (Ohio) Tribune. From radio + -thon, after telethon.

Pronunciation

radiothon

/ˈreɪdɪə(ʊ)θɒn/