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 problem of longevity possesses philosophical and practical contradictions, now heightened by the gradual disappearance of artists of Serra’s generation and the uncertain posthumous legacy of their work. — Jeffrey Weiss, Artforum, 1 Oct. 2026

His uncertain fate plays out in the present-day imagination of an unnamed curator of unspecified gender, who has been employed by the palace to dress some of its rooms for public viewing in the wake of an undescribed personal tragedy. — Literary Hub, 1 Oct. 2026

Gretchen ends up surviving the movie, because Donnie goes back in time and saves her, but her future is left uncertain. — Louis Peitzman, Vulture, 1 Oct. 2026

The project faces uncertain costs, a timeline that could push exports beyond 2028 and possible legal challenges. — Los Angeles Times, 30 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