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unreliable
/ˌʌnrɪˈlaɪəbəl/
not trustworthy
The weather forecast was unreliable, so we got caught in the rain.
The forecast could not be trusted, leading to an unexpected situation.
general
not able to be trusted or depended on
The old car is unreliable and breaks down frequently.
The car cannot be depended on to function properly.
She found the witness's testimony unreliable due to inconsistencies.
The witness could not be trusted because their statements were contradictory.
Often used to describe people, systems, or information that fail to meet expectations consistently.
Collocations
unreliable sourcea source that cannot be trustedunreliable servicea service that does not work consistentlyunreliable datadata that is not accurate or consistent
Pro Tip
Avoid overusing 'unreliable'
While 'unreliable' is useful, try to be specific about why something is unreliable (e.g., 'The GPS is unreliable in rural areas' instead of just saying it's unreliable).
Gold Rule
Use 'unreliable' for consistent failure
Reserve 'unreliable' for things that fail repeatedly, not for one-time mistakes. For example, 'The bus is unreliable' implies it is often late or breaks down, not just that it was late once.
Word Origin
From Middle English 'un-' (not) + 'rely' (to depend on) + '-able' (capable of being). First recorded in the 16th century.
Usage Notes
Commonly used in everyday contexts to describe people, machines, or information that do not perform as expected. Avoid using it in formal contexts where 'untrustworthy' or 'undependable' may sound more professional.
Word Breakdown
un-
not
prefixrely
to depend on
root-able
capable of being
suffixEnglish Dictionary