unsubstantiated

adjective

un·​sub·​stan·​ti·​at·​ed ˌən-səb-ˈstan(t)-shē-ˌā-təd 

: not proven to be true : not substantiated

an unsubstantiated rumor/report

a plausible but unsubstantiated theory

Synonyms of unsubstantiated

• unreasonable
• unfounded
• baseless
• unsupported

Examples of unsubstantiated in a Sentence

an unsubstantiated claim that was thrown out of court

Recent Examples on the Web

China has denied the espionage allegations, calling them unsubstantiated and an attempt to smear the country. — Steve Mollman, MSNBC Newsweek, 9 Nov. 2026

Blades Brown was in the field in Mexico and finished a respectable T-19, and during the event, an unsubstantiated yet absolutely hysterical rumor about the teenage phenom made the rounds in the golf world. — Mark Harris Outkick, FOXNews.com, 2 Nov. 2026

Netanyahu’s unsubstantiated claims of election interference have drawn swift rebukes, as the opposition considers using its numbers to shape the Knesset before a new government is formed. — Cara Anna, Los Angeles Times, 30 Oct. 2026

Bolsonaro has refused to concede defeat and has made unsubstantiated accusations of election fraud. — Matthew Lee, Arkansas Online, 28 Oct. 2026

Word History

First Known Use

circa 1775, in the meaning defined above

Rhymes for unsubstantiated

• abbreviated
• accelerated
• accentuated
• accommodated
• acculturated
• accumulated
• acidulated
• adjudicated
• administrated
• adulterated
• affiliated
• agglomerated