unreliable

adjective

un·​re·​li·​able ˌən-ri-ˈlī-ə-bəl 

: not reliable : undependable, untrustworthy

an unreliable friend

an unreliable source of funding

an unreliable car

unreliability

ˌən-ri-ˌlī-ə-ˈbi-lə-tē 

noun

the unreliability of the data

a person with a reputation for unreliability

unreliably

ˌən-ri-ˈlī-ə-blē 

adverb

a method that works unreliably

Examples of unreliable in a Sentence

Recent Examples on the Web

Fuel is costly and polluting, and the generators provide limited, unreliable power. — ABC News, 6 Oct. 2026

An access procedure that worked for 50 employees may become unreliable at 500. — Sami Nomair, Forbes.com, 5 Oct. 2026

This is encouraging — trustworthy system should be able to pump the breaks and realize when data inputs are too unreliable to make accurate estimations. — Euan Ashley, STAT, 1 Oct. 2026

The hurdle with optical signals, though, is that sunlight contains radiation in these wavelengths, which can interfere with optical signals and make transmission unreliable and difficult. — Ameya Paleja, Interesting Engineering, 1 Oct. 2026

Word History

First Known Use

1810, in the meaning defined above

Rhymes for unreliable

• liable
• pliable
• triable
• viable
• classifiable
• justifiable
• modifiable
• notifiable
• satisfiable
• specifiable
• undeniable
• verifiable