unreliable

Adjective

• lacking a sense of responsibility

• dangerously unstable and unpredictable
  • treacherous winding roads
    
  • an unreliable trestle
    

• not worthy of reliance or trust
  • in the early 1950s computers were large and expensive and unreliable
    
  • an undependable assistant
    

• liable to be erroneous or misleading
  • an undependable generalization
    

Related words

• Synonyms: 
  treacherous , undependable
• Antonyms: 
  reliable , dependable