blue

n

1. sky, blue skies, empyrean, firmament, vault of heaven, azure deeps, Chiefly Literary. welkin; the air, the atmosphere.

2. out of the blue

suddenly, unexpectedly, all of a sudden. See suddenly (def.1).

adj

3. sky-blue, baby-blue, powder-blue, deep-blue; azure, sapphire, cyan blue, aquamarine, turquoise, marine blue, ultramarine, lapis lazuli, navy, indigo.

4. depressed, despondent, morose, doleful, dispirited, unhappy, sad, downcast, glum; dismal, bleak, gloomy, depressing, dispiriting.

5. righteous, puritanical, moralistic, severe, strict, rigid, prudish.

6.Informal. indecent, risque, bawdy, obscene, Inf. dirty; vulgar, coarse, offensive, improper.