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

The opposition’s small lead initially was uncertain but was confirmed after early votes that didn’t arrive at polling stations by Election Day, including overseas ballots, were counted. — ABC News, 17 Sep. 2026

The opposition’s small lead was initially uncertain but was confirmed after early votes that didn’t arrive at polling stations by Election Day, including overseas ballots, were counted. — Los Angeles Times, 17 Sep. 2026

Sheeran was eight months into his Loop Tour, but after two dates in New Jersey — both featuring Macklemore — the fate of the rest of its North American leg was suddenly uncertain. — Shirley Halperin, Rolling Stone, 17 Sep. 2026

Asking an 18- or 21-year-old athlete to sacrifice some portion of a present opportunity for an uncertain benefit that may principally accrue to someone else five or 10 years in the future is an inherently difficult organizing proposition. — Chris Corr, Sportico.com, 17 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