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

Internal affairs complaints The lawsuit identifies five internal complaints filed against Sumstad between December 2022 and October 2025 and alleges each was dismissed, deemed unsubstantiated or ended in her exoneration. — Ben Wheeler, Kansas City Star, 24 Sep. 2026

Somehow this unsubstantiated story became internationally known with almost no major media explicitly reporting it, and before the modern version of the internet. — Allen Salkin, HollywoodReporter, 14 Sep. 2026

Some Democrats fear Trump could use those unsubstantiated assertions as a pretext to intervene in November. — Susan Page, USA Today, 1 Sep. 2026

Many are leaning into their own unsubstantiated suppositions, even those not backed by evidence. — Rebekah Riess, CNN Money, 22 Aug. 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