'out of the blue' definitions:

Definition of 'out of the blue'

(from WordNet)
adverb
In a way that was not expected; "her brother showed up at the wedding out of the blue" [syn: unexpectedly, 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" [syn: unanticipated, unforeseen, unlooked-for, out of the blue(p)]

Synonyms of 'out of the blue'

From: Moby Thesaurus

Words containing 'out of the blue'