Synonyms of unsubstantiated

unsubstantiated

adjective

ˌən-səb-ˈstan(t)-shē-ˌā-təd 

as in unreasonable

having no basis in reason or fact

an unsubstantiated claim that was thrown out of court

Synonyms & Similar Words

• unreasonable
• unfounded
• baseless
• unsupported
• unwarranted
• groundless
• irrational
• false
• invalid
• unreasoned
• unnecessary
• misleading
• absurd
• illogical
• fallacious
• foundationless
• inconsistent
• implausible
• nonvalid
• weak
• specious
• meaningless
• unconvincing
• misled
• unconscionable
• untenable
• wrong
• gratuitous
• unsound
• flimsy
• stupid
• uncalled-for
• nonsensical
• foolish
• fatuous
• nonlogical
• preposterous
• silly
• asinine
• insane
• ill-advised
• unwise
• wacky
• simpleminded
• harebrained
• nutty
• mad
• crackpot
• senseless
• brainless
• crazy
• half-witted

Antonyms & Near Antonyms

• reasonable
• valid
• good
• justified
• hard
• reasoned
• confirmed
• just
• substantiated
• certified
• well-founded
• logical
• rational
• informed
• well-grounded
• actual
• true
• real
• validated
• sensible
• wise
• certain
• genuine
• verified
• corroborated
• sane
• sober
• sure
• clear
• plausible
• solid
• credible
• compelling
• convincing
• sound
• persuasive
• commonsense
• satisfying
• cogent

Example Sentences

Recent Examples of unsubstantiated

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

The company alleged Fox broadcasted unsubstantiated allegations that Dominion's software manipulated vote counts, and the news organization settled for $787 million. — Aki Nace, CBS News, 24 June 2026

On Facebook, TikTok and Instagram, unsubstantiated claims often go unchecked. — Duaa Eldeib, ProPublica, 12 June 2026