Lacking substantiation; without evidence.

A divesting of substantiality.

That cannot be substantiated.

present participle of unsubstantiate

Lacking substance; insubstantial. / Unsubstantiated; unproven.

Third-person singular simple present indicative form of unsubstantiate

To prove false; to disprove or discredit. / (human services) To officially categorize (an allegation) as unsubstantiated. / To call into question; to create doubt about.