impossible to be continued or supported
untenable - unsustainable
If something is ‘untenable’, it cannot be defended, justified, or maintained. It is used when a position or situation reaches a breaking point where circumstances mean you have to abandon something or do something you’d rather not. It is a formal word which is most commonly seen in written English, such as in an official document or newspaper article.
The other members of staff have made it clear that they do not want to work with me. That puts me in an untenable position, so I will have to resign.
I originally defended Alice from the accusation, but when new damning evidence emerged, my support for her became untenable.
The situation the business is in now is untenable. If things don’t quickly turn around, we will have to close down.