Definition of out of the blue in US English:

out of the blue

(also out of a clear blue sky)

phrase

informal
  • Without warning; unexpectedly.

    ‘she phoned me out of the blue’
    • ‘As for how the opportunity was spotted, it was a complete bolt out of the blue.’
    • ‘It always comes slamming down out of a clear blue sky, unplanned and unforeseen.’
    • ‘The government's interest in sexual health has not come out of the blue.’
    • ‘Rarely does a profit warning come out of the blue like the subsequent share price reaction suggests.’
    • ‘After six weeks the trail seemed to be going cold when a phone call came out of the blue.’
    • ‘Then, last month, I got a phone call out of the blue from one of the photo managers at Head Office.’
    • ‘He was working as a meat products salesman during the 1960s, when his chance to run the pub came out of the blue.’
    • ‘Now, out of the blue, my own bank, write to me to tell me that they may have inadvertently ripped me off.’
    • ‘He called me yesterday, out of the blue, basically to offer me some work.’
    • ‘Stephen phoned out of the blue, haven't spoken to him in over three months!’
    • ‘This came out of the blue, and we are most upset that a warning wasn't given.’
    • ‘This hasn't been done out of the blue and they have been given every chance to stop doing it.’
    • ‘Because all of a sudden, almost out of the blue, the summer had ended and college was the immediate future.’
    • ‘His was a performance out of the blue but one that he certainly can repeat again as he grows in confidence.’
    • ‘This particular warning came out of the blue and there must be a worry that there is yet more to come.’
    • ‘The yellow card came out of the blue and I do not believe there was any warning from the referee.’
    • ‘Philip's voice is completely casual, like he's just had this sudden thought out of the blue.’
    • ‘Than he calls me up kind of out of the blue and it's just this weird, random kind of thing.’
    • ‘It's a bit worrying because this guy actually knows where I live and has dropped round out of the blue but not for a long time.’
    • ‘Quite frankly, this piece of research is so unexpected, so out of the blue, it beggars belief.’