Unverifiable (adjective)

1. Not capable of being confirmed or proven to be true.
2. Not able to be verified or substantiated.

Origin:

Derived from the word 'verify' meaning to confirm or prove something to be true.

Examples:

1. The claim was unverifiable and therefore not considered credible.
2. His alibi was unverifiable, he was the only one who could confirm it.
3. The theory was unverifiable, there was no way to test it.
4. The information was unverifiable, it was not supported by any evidence.
5. The results were unverifiable, they could not be repeated in another experiment.