Expressions used in Everyday Spoken English in Social and Professional contexts
Something which is unsubstantiated is not supported by facts or not proven to be true. Something described as being 'unsubstantiated' might just be a rumour or a claim made without any evidence to back it up. Unsubstantiated is similar in meaning to 'unconfirmed' 'uncorroborated' or 'unsupported'. This is an adjective used often in academic and legal contexts.