Synonyms of 'unsubstantiated'
unconfirmedDictionary, unproven, unsupported
unsubstantiated rumours about his private life
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If you say that a fear, accusation, or story is groundless, you mean that it is not based on evidence and is unlikely to be true or valid.
A ministry official described the report as groundless.
Thesaurus for unsubstantiated from the Collins English Thesaurus
A claim , accusation , or story that is unsubstantiated has not been proved to be valid or true .