/blu: ||; blu/noun1 [C,U] the colour of a clear sky when the sun shines 蓝色;蔚蓝色: a deep blue 深蓝色dressed in blue(= blue clothes) 穿着蓝色衣服
2 the blues [pl] [with.sop] a type of slow sad music 布鲁斯音乐,蓝调(一种伤感而缓慢的音乐): a blues singer 布鲁斯歌手
3 the blues [pl] (informal 非正式) a feeling of great sadness; depression 忧郁;沮丧: to have the blues 闷闷不乐
out of the blue suddenly; unexpectedly 突如其来;晴天霹雳:
I didn't hear from him for years and then this letter came out of the blue. 多年来他音信全无,现在却突然给我来了这封信。