out of the blue

Adjective

• not anticipated
  • unanticipated and disconcerting lines of development- H.W.Glidden
    
  • unforeseen circumstances
    
  • a virtue unlooked-for in people so full of energy
    
  • like a bolt out of the blue
    

Adverb

• in a way that was not expected
  • her brother showed up at the wedding out of the blue
    

Related words

• Synonyms: 
  unanticipated , unforeseen , unlooked-for , out of the blue(p) , unexpectedly