Synonyms of out of the blue

Adjective

1. unanticipated, unforeseen, unlooked-for, out of the blue(predicate), unexpected (vs. expected)

usage: 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

1. unexpectedly, out of the blue

usage: in a way that was not expected; "her brother showed up at the wedding out of the blue"