untenable

Not capable of being maintained or defended.

Not capable of being occupied or lived in.

Insupportable; intolerable.

Not tenable; that cannot be held in possession: as, an untenable post or fort. That cannot be maintained by argument; not defensible: as, an untenable doctrine.

Not able to be held, as of an opinion or position; unholdable, indefensible.

(of theories etc) incapable of being defended or justified