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

My hope is for compassion, healing, and reflection at a time that is becoming one of the darkest and most uncertain periods in our nation's history. —Wcco Staff, CBS News, 9 Jan. 2026

But whether the new law will meaningfully reduce electric bills remains uncertain. —Jeremy Gorner, Chicago Tribune, 9 Jan. 2026

Whether Reza Pahlavi can sustain influence remains uncertain. —Cnn Staff, CNN Money, 9 Jan. 2026

At a time when life can sometimes feel fragmented or uncertain, the Christmas season invites us to remember the power of reaching out to one another with generosity of heart, understanding and hope. —Meredith Kile, PEOPLE, 9 Jan. 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