There are 2 main definitions of blue in English:


Syllabification: blue
Pronunciation: /blo͞o

adjective (bluer, bluest)

1Of a color intermediate between green and violet, as of the sky or sea on a sunny day: the clear blue sky a blue silk shirt deep blue eyes
More example sentences
  • At the age of seventy, his blue eyes still twinkle under a mop of corkscrew curls.
  • The sun was up, the sky was blue, there wasn't a cloud to spoil the view.
  • The water was quite calm and the sky was blue.
sky blue, azure, cobalt, sapphire, navy, powder blue, midnight blue, Prussian blue, electric blue, indigo, royal blue, ice-blue, baby blue, air force blue, robin's egg blue, peacock blue, ultramarine, aquamarine, steel blue, slate blue, cyan;
chiefly British Oxford blue, Cambridge blue
literary cerulean
1.1(Of a person’s skin) having turned blue as a result of cold or breathing difficulties: Annie went blue, and I panicked
More example sentences
  • There may also be obvious cyanosis (when the lips and/or skin appears blue due to lack of oxygen in the blood).
  • Victims suffered from acute cyanosis, a blue discoloration of the skin and mucous membranes.
  • She turned blue whenever she cried, and the doctor said it would be a miracle if she lived past her first month.
1.2(Of a bird or other animal) having blue markings: a blue jay
More example sentences
  • Animals include duikers, eland and colobus, vervet and blue monkeys.
  • According to zoology, the origin of blue bull is not traced to the species of cow.
  • I should have told you in previous episodes that anger is characterised by a red bear, sloth by a light blue goat, and avarice by a yellow frog.
1.3(Of cats, foxes, or rabbits) having fur of a smoky gray color: the blue fox
More example sentences
  • She admires the drawing above the oven: a drawing of the blue fox howling at the moon.
  • He grabs the shredded pieces of his drawing: the blue fox howling at the moon.
  • He was a blue cat named Paul, a sweet little fellow with a pleasant disposition.
1.4(Of a ski run) of the second lowest level of difficulty, as indicated by colored markers positioned along it.
More example sentences
  • There are just a few chair lifts that end where the blue trail crosses the cliff.
  • And to return to the southern lodge, forget it, you are forced with either a black trail or a long and very challenging blue trail.
  • Last year the trail was rated blue (moderate) and the rating for this next year is not decided yet.
1.5 Physics Denoting one of three colors of quark.
More example sentences
  • So for instance, we could start off with a red quark, which emits a red-antiblue gluon and becomes a blue quark.
  • For example, if absorption of a gluon changes a blue quark into a red quark, then the gluon itself must have carried one unit of red charge and minus one unit of blue charge.
  • This blue quark will become red and the original red quark will become blue.
2 informal (Of a person or mood) melancholy, sad, or depressed: he’s feeling blue
More example sentences
  • Deep in their own blue mood, they're unaffected by people or events that are going on around them.
  • The blue mood of yesterday seems to have lifted a little.
  • Maybe the rain brings more blue mood for me and a three year anniversary reminds me to look back to see what happened in the days before.
3 informal (Of a movie, joke, or story) with sexual or pornographic content: the blue movies are hugely profitable
More example sentences
  • Video cassettes showing blue films and cinema houses lost out to the village gurdwara.
  • We have the same sort of content as the women's classes but there is the odd slightly blue joke, too.
  • Would you be content with watching a blue movie instead of doing the real thing?
3.1(Of language) marked by cursing, swearing, and blasphemy.
More example sentences
  • Erik cursed a blue streak in French under his breath before picking up his suitcase and heading for the door.
  • Well, that day in the woods as I cursed a blue streak, he stood by, smiling and laughing at me.
  • The cameras spend the rest of the inning cutting to shots of him in the dugout, cursing a blue streak at himself.
4 informal dated Rigidly religious or moralistic; puritanical.
More example sentences
  • With the dissolution of the Puritan theocracies after the American Revolution, blue laws declined; many of them lay forgotten in state statute books only to be revived much later.
  • Keep in mind most states have blue laws that are typically unenforced unless they want to pile it on to someone who is otherwise being bad.
  • For those of you that don’t know, “blue laws” they were set up to prohibit, under penalty of law, items from being purchased on Sundays.


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1Blue color or pigment: she was dressed in blue the dark blue of his eyes armchairs in pastel blues and greens
More example sentences
  • As one would stare upwards, the sky would change from red, to orange, to green, to dark blue, to royal purple.
  • Using strong colours like dark blue, deep reds and yellows, her work is certainly striking.
  • All samples are shown at the same magnification, with spindles in green and DNA in blue.
1.1Blue clothes or material: Susan wore blue
More example sentences
  • The old man was robed in deep blue with a cloak of the same purple the guards wore.
  • Andrew, wearing all blue, created by metallic clothing, walks into a small office.
  • She wore a gown of startling blue, hinting that her name should have been Sapphire.
1.2 (usually Blue) The Union army in the Civil War, or a member of that army.
[because Union soldiers wore blue uniforms]
2A blue thing, in particular.
2.1A blue ball, piece, etc., in a game or sport.
More example sentences
  • Use blue if you have games for five year olds and brown if your visitors are color-blind.
  • Lucian chooses the red piece, I choose blue, and we spend a good two hours sitting on the floor.
  • Speak took the yellow and green and doubled the brown to keep his chances alive, but missed the blue.
2.2 (the blue) literary The sky or sea; the unknown: a lark went trilling up, up into the blue
More example sentences
  • A single tiny cloud appeared above the ridge but soon dissolved into the blue.
  • Check your charts, your boat and supplies, then head out into the blue.
  • Sitting on the cold soft sand on the deserted beach I stared out into the blue.
3 [usually with modifier] A small butterfly, the male of which is predominantly blue while the female is typically brown.
More example sentences
  • The male blues show much more interest in these yellow bushes.
  • As caterpillars, the blues are carefully cleaned and fed.
  • A cool day in midsummer is always a good day to watch blues taking shelter in the grass.
4 another term for bluing.
More example sentences
  • This laundry starch company began producing laundry blue in 1852 by using a combination of a synthetic ultramarine and sodium bicarbonate.
  • Industry had already understood before the First World War how to make time-consuming bleaching a thing of the past by inventing laundry blue, a powder based on indigo.
  • At the same time he discovered laundry blue.

verb (blues, bluing or blueing, blued)

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1Make or become blue: [with object]: the light dims, bluing the retina (as adjective blued) blued paper [no object]: the day would haze, the air bluing with afternoon
More example sentences
  • I was up all night listening to music when a light blued the east, announcing the season of breakfast.
  • The atmosphere in this video is darkened yet strangely luminous, the video palette seemingly blued and grayed.
  • All there were were tiny wisps of clouds now and the whole area had blued out.
1.1 [with object] Heat (metal) so as to give it a grayish-blue finish: (as adjective blued) nickel-plated or blued hooks
More example sentences
  • All in all, it is an attractive rifle, with nicely blued metal contrasting with an attractive piece of walnut.
  • The hammer, trigger, and trigger guard are also blued to a mirror-like finish, and the sides of the frame sport a somewhat subdued finish, contrasting nicely with the rest of the gun.
  • Having owned several and examined many others I see no difference in terms of overall fit and finish, metal polishing and bluing, or action smoothness.
2 [with object] Wash (white clothes) with bluing.
More example sentences
  • She would blue the laundry / For the children.
  • Washing was a long involved process which started with making the soap using lye, lard and ashes, then scrubbing, boiling, rinsing and bluing the clothes in huge outdoor vats of water.
  • A couple of wooden benches at the side of the house in the shade held 3 big galvanized iron tubs for washing, rinsing and bluing the clothes, and a tin dish for the starch.


Middle English: from Old French bleu, ultimately of Germanic origin and related to Old English blǣwen 'blue' and Old Norse blár 'dark blue'.


do something until (or till) one is blue in the face

informal Put all one’s efforts into doing something to no avail: she could talk to him until she was blue in the face, but he was just not hearing
More example sentences
  • Obviously, we could sit here and talk until we're blue in the face about how wonderfully they play the game.
  • I complained and complained and complained until I was blue in the face.
  • I could tell him till I was blue in the face that we had to leave, he does not understand, he is not from here.

men in blue

informal Police officers.
hardly ever, scarcely ever, rarely, very seldom

once in a blue moon

informal Very rarely.
[because a “blue moon” is a phenomenon that occurs rarely]
More example sentences
  • The young lad soundly decided to go along with these men, knowing that an opportunity like this came once in a blue moon or maybe even rarer.
  • I don't expect any body to start reading the amount of books that I do, such people only come around once in a blue moon, they are out there but I they don't usually advertise to the world the freaks that we are.
  • She said: ‘I only go to bingo once in a blue moon and it was a spur of the moment decision to go on Saturday afternoon.’

out of the blue

(or out of a clear blue sky)
informal Without warning; unexpectedly: she phoned me out of the blue
[with reference to a “blue” (i.e., clear) sky, from which nothing unusual is expected]
More example sentences
  • Rarely does a profit warning come out of the blue like the subsequent share price reaction suggests.
  • Quite frankly, this piece of research is so unexpected, so out of the blue, it beggars belief.
  • This particular warning came out of the blue and there must be a worry that there is yet more to come.

talk a blue streak

North American informal Speak continuously and at great length.
More example sentences
  • Reading it is like trying to keep up with a fast walker who is also talking a blue streak.
  • Unfortunately I know very little about them because I talked a blue streak from the moment they stepped in the door to the moment the door closed behind them when they left.
  • She hadn't slept for three days, and talked a blue streak.



More example sentences
  • But the real high point is nothing, really - just a moment when he forgets all his tensions about red carpets and movies, and suddenly notices a beautiful old Edwardian boat moored in the unbelievable blueness of the bay.
  • The blueness of the glass and the sunshine works really well with the wave.
  • Above the rows of houses, the blueness brings hope.

Definition of blue in:

There are 2 main definitions of blue in English:


Line breaks: blue

Entry from British & World English dictionary

verb (blues, bluing or blueing, blued)

British informal , dated
Squander or recklessly spend (money).


mid 19th century: perhaps a variant of blow1.

Definition of blue in: