1. out of the blue, unanticipated, unforeseen, unlooked-for

not anticipated

Example Sentences:
'unanticipated and disconcerting lines of development'
'unforeseen circumstances'
'a virtue unlooked-for in people so full of energy'
'like a bolt out of the blue'

• unanticipated
• unforeseen
• unlooked-for

2. out of the blue, unexpectedly

in a way that was not expected

Example Sentences:
'her brother showed up at the wedding out of the blue'

• unexpectedly