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

• capricious
• changeable
• changeful
• fickle
• flickery
• fluctuating
• fluid
• inconsistent
• inconstant
• mercurial
• mutable
• skittish
• temperamental
• unpredictable
• unsettled
• unstable
• unsteady
• variable
• volatile

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

TikTok’s viability had been uncertain since then-President Trump moved to shut it down in 2020, citing national security concerns. —Stacy Perman, Los Angeles Times, 19 Jan. 2025

While Hoyer’s fate is uncertain, the return of Sosa brought some new life to an often stale product — the annual Cubs Convention. —Paul Sullivan, Chicago Tribune, 18 Jan. 2025

While much is currently uncertain, the threats to the GS segment seem, at this moment, overblown. —Kenneth Squire, CNBC, 18 Jan. 2025

However, whether that argument would work in court is uncertain, according to Rozenshtein. —Aysha Bagchi, USA TODAY, 18 Jan. 2025

Word History

First Known Use

14th century, in the meaning defined at sense 3

Phrases Containing uncertain

• in no uncertain terms

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