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

How to stop constantly looking forward at an uncertain tomorrow, at least momentarily, and go back in time precisely when we’re told that history is over? —Jonathan Odden, Artforum, 2 June 2026

Emancipation was uncertain also. —Literary Hub, 2 June 2026

While adding a new monthly bill to the mix may feel counterintuitive, there's a strong case to be made for reevaluating select insurance types now, in the uncertain economic climate many now find themselves in. —Matt Richardson, CBS News, 1 June 2026

Instead, Democrats focused on the state failing to meet the state’s obligation in the school funding formula, funding schools with uncertain lottery funds and the state contributing more money to the Missouri Scholars Program, which can contribute money toward private school tuition. —Jack Harvel, Kansas City Star, 1 June 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