unreliable
gb/ˌʌnɹɪlˈaɪəbəl/ us/ˌʌnɹɪlˈaɪəbəl/
B2
English
Senses
0 senses
adjective
B2
property
1
not dependable as a person
Someone who is unreliable often does not do what they promise.
Usage pattern:
unreliable [person/employee/friend]
Common mistake:
Learners sometimes use unreliable to mean 'unavailable' or 'busy'; it mainly means 'not dependable'.
Synonyms
undependable (Direct synonym; emphasizes lack of consistency.)
|
untrustworthy (Suggests you cannot trust their honesty, not just their punctuality.)
|
inconsistent (Focuses on changing behavior rather than character.)
Antonyms
reliable (Can be trusted to do what is expected.)
|
dependable (Emphasizes steady support and responsibility.)
Collocations
an unreliable person
|an unreliable employee
|an unreliable friend
|highly unreliable
|rather unreliable
|prove unreliable
|become unreliable
|unreliable at work
|unreliable with money
|unreliable in a crisis
Themes
relationships
|work
|daily_life
Examples
- He's talented, but he's unreliable and often misses deadlines.
- I stopped asking her for help because she’s too unreliable.
- They need someone reliable, not an unreliable partner who disappears for days.
Learner examples
- My bus driver is unreliable.
- He is unreliable, so I don’t trust him.
adjective
B2
property
2
not working consistently
Something unreliable does not work well all the time.
Usage pattern:
unreliable [car/machine/service/connection]
Common mistake:
Unreliable describes performance over time; for a single failure, learners may prefer 'broken' or 'not working'.
Synonyms
faulty (Emphasizes a defect or technical problem.)
|
temperamental (Suggests it works sometimes but is unpredictable.)
|
erratic (Highlights irregular, unpredictable performance.)
Antonyms
reliable (Works well and consistently.)
|
stable (Emphasizes steady, predictable performance (often for systems).)
Collocations
an unreliable car
|unreliable equipment
|unreliable service
|unreliable internet
|an unreliable connection
|unreliable public transport
|an unreliable engine
|unreliable software
|unreliable power supply
|unreliable delivery
Themes
technology
|daily_life
|transport
Examples
- Their old car is unreliable and keeps breaking down.
- The Wi‑Fi is unreliable in this building, so video calls often drop.
- We replaced the printer because it was too unreliable.
Learner examples
- My phone is unreliable.
- The internet here is unreliable.
adjective
C1
property
3
not trustworthy as information
Information that is unreliable may be wrong.
Usage pattern:
unreliable [information/source/report/website]
Common mistake:
Learners may confuse unreliable with 'unknown'; something can be well-known but still unreliable.
Synonyms
dubious (Suggests there is good reason to doubt it.)
|
questionable (More neutral; implies it may not be trustworthy.)
|
untrustworthy (Often used for sources; can also suggest dishonest intent.)
Antonyms
reliable (Likely to be true and accurate.)
|
credible (Believable because it seems trustworthy.)
Collocations
an unreliable source
|unreliable information
|an unreliable report
|unreliable claims
|unreliable figures
|an unreliable website
|unreliable statistics
|unreliable testimony
|unreliable data
|highly unreliable
Themes
media
|education
|information
Examples
- Most of the information on that site is unreliable.
- The article relied on unreliable sources and contained several errors.
- Without records, any estimate would be unreliable.
Learner examples
- This news is unreliable.
- The source is unreliable.
adjective
C1
property
4
inconsistent or unpredictable results
If results are unreliable, they change a lot and you can’t depend on them.
Usage pattern:
unreliable [results/performance/measurements]
Common mistake:
Learners may use unreliable when they mean 'inaccurate'; unreliable can mean either inaccurate or simply inconsistent.
Synonyms
inconsistent (Emphasizes variation over time.)
|
erratic (Stronger; suggests sudden, unpredictable changes.)
|
variable (More neutral; common in technical or scientific contexts.)
Antonyms
consistent (Similar results over time.)
|
steady (Stable and not changing suddenly.)
Collocations
unreliable results
|unreliable performance
|unreliable measurements
|unreliable estimates
|unreliable indicators
|unreliable forecasts
|unreliable signals
|unreliable readings
|unreliable output
|unreliable quality
Themes
science
|business
|sports
Examples
- The test produced unreliable results, so they ran it again.
- His performance this season has been unreliable: brilliant one week, poor the next.
- Because of interference, the sensor gives unreliable readings.
Learner examples
- The results are unreliable.
- His work is unreliable.
Grammar
Dictionary form
unreliable
IPA
GB/ˌʌnɹɪlˈaɪəbəl/
US/ˌʌnɹɪlˈaɪəbəl/
Syllables & stress
un - re - li - able (4 syllables)
Stress on 3rd syllable (li)
Word forms
Adjective
- Base: unreliable
Expressions
unreliable connection
1/ˌʌnɹɪlˈaɪəbəl kənˈɛkʃən/
fixed phrase
internet link that often fails
A connection that stops or becomes weak often.
Examples
- I kept losing audio because of an unreliable connection.
- If you have an unreliable connection, it helps to turn off video during calls.
unreliable narrator
1/ˌʌnɹɪlˈaɪəbəl nˈɛɹeɪtɚ/
fixed phrase
Narrator who cannot be trusted
A narrator who does not tell the story in a fully true or clear way, so the reader cannot fully trust what they say.
Examples
- The twist ending reveals that the book has an unreliable narrator.
- An unreliable narrator makes the reader work harder to find the real story.
- Film critics praised the use of an unreliable narrator to create suspense.
unreliable narrator
1/ˌʌnɹɪlˈaɪəbəl nˈɛɹeɪtɚ/
fixed phrase
storyteller you cannot fully trust
A narrator who may not tell the truth or may be wrong.
Examples
- The novel uses an unreliable narrator, so the reader has to question every detail.
- Halfway through the film, you realize the narrator has been unreliable all along.
unreliable source
1/ˌʌnɹɪlˈaɪəbəl sˈɔɹs/
fixed phrase
source that cannot be trusted
A source that often gives wrong information.
Examples
- The story came from an unreliable source, so we didn’t publish it.
- Try to confirm the claim with a second source if the first one seems unreliable.
unreliable witness
1/ˌʌnɹɪlˈaɪəbəl wˈɪtnəs/
fixed phrase
legal
witness whose testimony is doubtful
A witness you cannot trust to give correct information.
Examples
- The defense argued that the key witness was unreliable.
- Because the witness changed his story, the jury saw him as an unreliable witness.