㉔out of the blue
意味：
予期せず。いきなり。前ぶれもなく突然。青天の霹靂。
Unexpectedly. By surprise. From nowhere.
例：
Out of the blue, he moved to a foreign country.
彼は突然、外国へ引っ越した。
She visited me out of the blue.
彼女はなんの前ぶれもなく訪ねてきた。
I didn't know he was seriously dating a girl.
