Definition

1. Adjective:
   • Not worthy of reliance or trust: Describes a person, thing, or source of information that cannot be depended on to perform consistently, accurately, or truthfully.
   • Dangerously unstable and unpredictable: Describes something that is not secure, steady, or safe, and whose behavior cannot be foreseen.
   • Liable to be erroneous or misleading: Describes information, data, or generalizations that are likely to be incorrect or give a false impression.

Usage and Examples

• Describing a person or assistant:
  • He is an unreliable employee; he often misses deadlines.
  • She proved to be an unreliable witness in court.
• Describing a machine, device, or system:
  • The old car is becoming unreliable and breaks down frequently.
  • Early computers were large and unreliable.
• Describing information or data:
  • The news from that website is often unreliable and full of rumors.
  • That is an unreliable generalization about the entire population.
• Describing a physical structure or conditions:
  • The bridge was old and unreliable.
  • The weather forecast for this region is notoriously unreliable.

Advanced Usage and Nuances

• "Unreliable narrator": A literary term for a storyteller (in a novel, film, etc.) whose credibility is compromised, often because they are deceptive, mentally unstable, or lack knowledge.
  • The novel uses an unreliable narrator to keep the reader guessing about the truth.
• In technical/engineering contexts: Refers to components or systems with a high probability of failure.
  • The experiment failed due to an unreliable power supply.

Variants and Related Words

• Unreliability (noun): The quality or state of being unreliable.
  • The unreliability of the public transport system is a major issue.
• Reliable (adjective): The direct antonym, meaning consistently good in quality or performance; able to be trusted.
  • She is my most reliable friend.

Synonyms

• Undependable: Not able to be relied on.
• Untrustworthy: Not deserving of trust.
• Erratic: Not even or regular in pattern or movement; unpredictable.
• Fickle: Changing frequently, especially in loyalties, interests, or affection.
• Fallible: Capable of making mistakes or being wrong.

Antonyms

• Reliable: Consistently good in quality or performance; able to be trusted.
• Dependable: Trustworthy and reliable.
• Trustworthy: Able to be relied on as honest or truthful.
• Stable: Not likely to change or fail; firmly established.

Idioms and Common Phrases

• Take with a grain of salt: This idiom is often used when referring to information from an unreliable source, meaning to view it with skepticism.
  • His account of events is unreliable, so you should take it with a grain of salt.

Adjective

1. lacking a sense of responsibility
2. dangerously unstable and unpredictable
   • treacherous winding roads
   • an unreliable trestle
3. not worthy of reliance or trust
   • in the early 1950s computers were large and expensive and unreliable
   • an undependable assistant
4. liable to be erroneous or misleading
   • an undependable generalization