Personally I call a project “discontinued” just when I know certainly that it will no longer receive updates by me in the future. But beware: not necessarily a discontinued project is equivalent to a program that no longer works. Simply, I repeat, it just means that it will no longer receive updates, but until there are no external changes in most cases the program will continue to work smoothly also for years.
A project in general could be discontinued for many reasons, but for me this has happened or will happen mainly for three different reasons:
As already said several times, a discontinued program will no longer receive any updates by me, in any case. So either you continue to use it, if possible, in spite of the bug or you just need to look for other equivalent programs on the web. Of course I ask you to avoid to send me requests for updates or bug reportings for discontinued projects, they will be completely ignored.