# unreliable

/ˌənɹiˈɫaɪəbəɫ/ (US) · /ˌʌnɹɪlˈaɪəbəl/ (UK)

Source: https://englishreference.com/word/unreliable
Updated: 2026-06-20

## Senses

### 1. not trustworthy or consistent

adjective · CEFR B1

not able to be trusted or depended on to do something well or to be true.

For teachers: lacking reliability; prone to failure, inconsistency, or inaccuracy.

- The bus service is very unreliable, so I usually walk to work instead.
- The witness was deemed unreliable by the prosecution after several major inconsistencies were discovered in her initial statement.

### 2. a person or thing that fails

noun · CEFR C2 · Formal

a person or thing that you cannot depend on.

For teachers: an entity, whether a person or a mechanical system, that consistently fails to perform as expected.

- Among all the new machines we bought, this one has been a total unreliable.
- The report identified the aging generator as a chronic unreliable, recommending its immediate replacement to avoid further power outages.

Usage: This noun use is much rarer than the adjective form and typically appears in formal or technical reports.

## Examples

- The old bus is unreliable and often breaks down.
- We cancelled the trip because the weather forecast was unreliable.
- Investors grew wary of the company after several quarters of unreliable financial reporting.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.