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

One Democrat member even made the unsubstantiated argument that laws to keep trans athletes out of girls' sports would result in genital inspections of children. —Jackson Thompson, FOXNews.com, 22 May 2025

Immigration authorities may reject frivolous or unsubstantiated cases. —Antonio Maria Delgado, Miami Herald, 19 May 2025

The agency investigated once but found the claims to be unsubstantiated, according to a state child welfare report cited by the outlet. —Brenton Blanchet, People.com, 9 May 2025

Last month, Ye was criticized for making comments about Jay-Z and Beyoncé’s 7-year-old kids Rumi and Sir Carter during an explosive X tirade, where West questioned the twins’ mental abilities and made unsubstantiated claims about in vitro fertilization. —Angel Diaz, Billboard, 21 Apr. 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