UNSUBSTANTIATED Synonyms: 92 Similar and Opposite Words

unsubstantiated

adjective

ˌən-səb-ˈstan(t)-shē-ˌā-təd

Definition of unsubstantiated

as in unreasonable

having no basis in reason or fact an unsubstantiated claim that was thrown out of court

Synonyms & Similar Words

Relevance

Antonyms & Near Antonyms

Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.

Recent Examples of unsubstantiated 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 In spite of the rhetoric and unsubstantiated claims, highways don’t equal economic development. — Pete Harrison, Hartford Courant, 6 July 2026 The former president has also made unsubstantiated claims of vandalism causing the pool's problems. — Bill Goodykoontz, AZCentral.com, 26 June 2026 See All Example Sentences for unsubstantiated

Recent Examples of Synonyms for unsubstantiated

Adjective

Your expectations of your stepsons aren’t unreasonable at all.

— R. Eric Thomas, Mercury News, 27 Aug. 2026
If the prosecution’s version of the evidence is reasonable and the defense’s is unreasonable, then that is not reasonable doubt.

— Christine Pelisek, PEOPLE, 25 Aug. 2026

Definition of unreasonable

Adjective

Towers said that concerns about consent and explanation of risk are baseless.

— Amy Yurkanin, ProPublica, 24 Aug. 2026
And Democratic aides in Washington are preparing members of Congress to push back in the court of public opinion against any baseless claims of voter fraud in competitive districts.

— Kevin Rector, Los Angeles Times, 23 Aug. 2026

Definition of baseless

Adjective

The lawsuit says the decision was unlawful, unsupported by facts and inconsistent with the military’s past praise of Claude.

— Reuters, NBC news, 28 Aug. 2026
The feedback is often vague, unsupported by concrete examples and disconnected from anything the employee could have reasonably corrected earlier.

— Lauren Russell, Forbes.com, 18 Aug. 2026

Definition of unsupported

Browse Nearby Words

unsubstantiality

unsubstantiated

unsubtle

See all Nearby Words

Cite this Entry

Style

“Unsubstantiated.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/unsubstantiated. Accessed 2 Sep. 2026.

Copy Citation

Synonyms of unsubstantiated

adjective

Example Sentences

Browse Nearby Words

Cite this Entry

More from Merriam-Webster

Word of the Day

dissonant

Popular in Grammar & Usage

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

A List of Most Commonly Confused Words

Why do we use apostrophes to show possession?

Is it 'nerve-racking' or 'nerve-wracking'?

What's the difference between 'fascism' and 'socialism'?

Popular in Wordplay

The Longest Long Words List

Stay Woke

Ye Olde Nincompoop: Old-Fashioned Words for 'Stupid'

14 Phobias You Probably Haven't Heard Of

Even More Bird Names that Sound Like Insults (and Sometimes Are)

Popular

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

The Longest Long Words List

Stay Woke

Games & Quizzes