An obsolete electronic service offering people the privilege of paying to read the weather on their television screens instead of having somebody read it to them for free while they brush their teeth.
The idea bombed everywhere it wasn't government-subsidised, because by the time videotex was practical the installed base of personal computers could hook up to time-sharing
services and do the things for which videotex might have been worthwhile better and cheaper. Videotex planners badly overestimated both the appeal of getting information from a computer and the cost of local intelligence at the user's end.
Like the gorilla arm
effect, this has been a cautionary tale to hackers ever since. See also vannevar