uncertain

adjective

un·​cer·​tain ˌən-ˈsər-tᵊn 

1

a

: not known beyond doubt : dubious

an uncertain claim

b

: not having certain knowledge : doubtful

remains uncertain about her plans

c

: not clearly identified or defined

a fire of uncertain origin

2

: not constant : variable, fitful

an uncertain breeze

3

: indefinite, indeterminate

the time of departure is uncertain

4

: not certain to occur : problematical

his success was uncertain

5

: not reliable : untrustworthy

an uncertain ally

uncertainly adverb

uncertainness

ˌən-ˈsər-tᵊn-(n)əs 

noun

Synonyms of uncertain

• volatile
• unpredictable
• changeful
• unstable
• inconsistent

Examples of uncertain in a Sentence

The time of departure is still uncertain.

We are still uncertain of the truth.

She remains uncertain about her plans.

I'm uncertain about how to respond.

The cause of the fire is uncertain.

He has an uncertain temper.

They face a financially uncertain future.

Recent Examples on the Web

Furthermore, similar efforts to advance heat protections in Springfield have stalled, with a heat protection bill getting sent back to the Illinois House Committee on Rules, leaving its future uncertain. — Maria Hadden, Chicago Tribune, 24 Sep. 2026

At the same time, markets are grappling with a central bank that suddenly has no interest in telegraphing its next moves, leaving an uncertain calculus on who is calling the shots — policymakers or market players. — Jeff Cox, CNBC, 24 Sep. 2026

James' lawsuit, however, said Polymarket's prediction markets meet the legal definition of gambling because the outcomes of the events on which its users are betting are uncertain and outside the control of the bettor, or hinge on a game of chance. — Aaron Katersky, ABC News, 24 Sep. 2026

Ahead of an uncertain offseason, the Mets are shoring up their staffing situation, adding Derek Falvey as a senior advisor of baseball operations, and promoting Kriss Gross to assistant general manager of scouting. — Abbey Mastracco, New York Daily News, 24 Sep. 2026

Word History

First Known Use

14th century, in the meaning defined at sense 3

Phrases Containing uncertain

• in no uncertain terms

Rhymes for uncertain

• bertin
• certain
• curtain

Kids Definition

uncertain

adjective

un·​cer·​tain ˌən-ˈsərt-ᵊn 

ˈən-

1

: not definite or fixed

an uncertain quantity

2

a

: not sure

uncertain of the truth

b

: not known for sure

an uncertain claim

3

: likely to change : not dependable

uncertain weather

uncertainly adverb