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

• baseless
• foundationless
• groundless
• invalid
• nonvalid
• unfounded
• unreasonable
• unsupported
• unwarranted

Examples of unsubstantiated in a Sentence

an unsubstantiated claim that was thrown out of court

Recent Examples on the Web

But an outside agency such as the Texas Rangers would not have access to unsubstantiated claims of misconduct by jailers when investigating a death in the Tarrant County jail. —Cody Copeland, Fort Worth Star-Telegram, 16 Apr. 2025

The statement served as a pointed rebuke to a president who had continued to make unsubstantiated allegations of voting fraud while Trump's legal team pursued multiple legal challenges in battleground states. —Josh Meyer, USA Today, 9 Apr. 2025

Stocks briefly rose yesterday on unsubstantiated reports that the administration might pause the tariffs for 90 days. —German Lopez, New York Times, 8 Apr. 2025

In light of all of this, biotech companies should be prepared to clearly articulate how their innovations translate into clinical outcomes, rather than relying on broad, unsubstantiated claims. —Niven R. Narain, Forbes.com, 31 Mar. 2025

Word History

First Known Use

circa 1775, in the meaning defined above

Rhymes for unsubstantiated

• ameliorated
• decontaminated
• deoxygenated
• deteriorated
• differentiated
• disarticulated
• excommunicated
• incapacitated
• individuated
• misappropriated
• monounsaturated
• multinucleated