untenable
[adjective]
Synonyms: unsustainable, groundless, illogical, indefensible, insupportable, shaky, unsound, weak

[TahlilGaran] English Synonym Dictionary ▲

un‧ten‧a‧ble /ʌnˈtenəbəl/ adjective formal

1. an untenable situation has become so difficult that it is impossible to continue:
The scandal put the President in an untenable position.

2. an untenable argument, suggestion etc is impossible to defend

[TahlilGaran] Dictionary of Contemporary English ▲