unsubstantiate

Short definition from Wiktionary

Verb

1. 1
   To prove false; to disprove or discredit.
2. 2
   To officially categorize (an allegation) as unsubstantiated.
3. 3
   To call into question; to create doubt about.
4. 4
   To make insubstantial or abstract; unsubstantialize.

Adjective

1. 1
   Lacking substance; insubstantial.
2. 2
   Unsubstantiated; unproven.