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

Trump has continued to make unsubstantiated claims that the 2020 election was stolen from him. — Rebecca Morin, USA Today, 16 July 2026

Those efforts were aided by Canary Mission and Betar, two pro-Israel groups that maintain online lists of Israel’s critics, often alongside unsubstantiated claims that they are affiliated with Hamas, according to the lawsuit. — Jake Offenhartz, Fortune, 15 July 2026

Conjecture over that evidence has fueled unsubstantiated conspiracy theories that there might have been a second shooter or that Kirk’s death was staged. — Hannah Schoenbaum, Chicago Tribune, 11 July 2026

Yoon, who faces other criminal cases as well, has promoted unsubstantiated election fraud claims circulated on YouTube to defend his botched power grab and rally conservative supporters against the Democrats. — ABC News, 7 July 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