out of the blue:出乎意料;突然;晴天霹雳 His resignation came right out of the blue. 他的辞职来得很突然.she had no idea that anything was wrong until he announced out of the blue that he wanted a divor
rack one's brains to try very hard to think of something 绞尽脑汁,苦思冥想I've been racking my brains all day trying to remember his name.我一整天都绞尽脑汁,想要回忆起他的名字.sidetrack:to make som