Untenable (adjective)

Not able to be held or defended; not sustainable or practical.

Origin:

From un- (not) + tenable (able to be held or defended).

Examples:

1. The position was untenable and the company had to change its strategy.
2. His argument was untenable and easily disproven.
3. The situation in the city had become untenable and the residents were forced to flee.
4. The defense was untenable and the team lost the match.
5. His position in the company became untenable after the scandal broke.