out of the blue

blue  (bl)

n.

1. The hue of that portion of the visible spectrum lying between green and indigo, evoked in the human observer by radiant energy with wavelengths of approximately 420 to 490 nanometers; any of a group of colors that may vary in lightness and saturation, whose hue is that of a clear daytime sky; one of the additive or light primaries; one of the psychological primary hues.

2.

a. A pigment or dye imparting this hue.

b. Bluing.

3.

a. An object having this hue.

b. Dress or clothing of this hue: The ushers wore blue.

4.

a. A person who wears a blue uniform.

b. blues A dress blue uniform, especially that of the U.S. Army.

5. often Blue

a. A member of the Union Army in the Civil War.

b. The Union Army.

6. A bluefish.

7. A small blue butterfly of the family Lycaenidae.

8.

a. The sky.

b. The sea.

adj. blu·er, blu·est

1. Of the color blue.

2. Bluish or having parts that are blue or bluish, as the blue spruce and the blue whale.

3. Having a gray or purplish color, as from cold or contusion.

4. Wearing blue.

5.

a. Gloomy; depressed. See Synonyms at depressed.

b. Dismal; dreary: a blue day.

6. Puritanical; strict.

7. Aristocratic; patrician.

8. Indecent; risqué: a blue joke; a blue movie.

tr. & intr.v. blued, blu·ing, blues

To make or become blue.

Idioms:

blue in the face

At the point of extreme exasperation: I argued with them until I was blue in the face.

into the blue

At a far distance; into the unknown: spontaneously take a trip into the blue.

out of the blue

1. From an unexpected or unforeseen source: criticism that came out of the blue.

2. At a completely unexpected time: a long-unseen friend who appeared out of the blue.

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[Middle English blue, bleu, from Old French bleu, of Germanic origin; see bhel-¹ in Indo-European roots.]

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bluely adv.

blueness n.

Thesaurus

Adj.	1.	out of the blue - 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" unanticipated, unforeseen, unlooked-for unexpected - not expected or anticipated; "unexpected guests"; "unexpected news"
Adv.	1.	out of the blue - in a way that was not expected; "her brother showed up at the wedding out of the blue" unexpectedly