the blue

WordReference Random House Learner's Dictionary of American English © 2026

blue /blu/   n., adj., blu•er, blu•est, v., blued, blu•ing or blue•ing. 
n. 

1. Physics [uncountable] the pure color of a clear sky;
   the primary color between green and violet.
2. [countable] something having a blue color.
3. the blue, [uncountable]
   • the sky:
     The plane shot off into the blue.
   • the sea:
     The boat sank into the deep blue.

adj. 

4. of the color blue:
   a beautiful blue sky.
5. sad or depressed in spirits:
   I'm feeling a little blue today, thinking about old friends.
6. [before a noun] holding or offering little hope;
   dismal;
   bleak:
   a blue outlook.
7. deriving from strict moral or religious observance;
   puritanical:
   [usually before a noun] Blue laws kept stores closed on Sundays.
8. indecent;
   off-color;
   obscene:
   a blue movie.

v. [~ + object]

9. to make (something) blue;
   dye (something) a blue color.

Idioms

10. Idioms blue in the face, at an extreme point of frustration, irritation, etc.:
    to argue till one is blue in the face.
11. Idioms out of the blue, suddenly and unexpectedly:
    Out of the blue, she inherited a fortune.

blue•ness, n. [uncountable] See blues.

WordReference Random House Unabridged Dictionary of American English © 2026

blue  (blo̅o̅), n., adj., blu•er, blu•est, v., blued, blu•ing or blue•ing. 
n. 

1. Physics the pure color of a clear sky;
   the primary color between green and violet in the visible spectrum, an effect of light with a wavelength between 450 and 500 nm.
2. bluing.
3. something having a blue color:
   Place the blue next to the red.
4. a person who wears blue or is a member of a group characterized by some blue symbol:
   Tomorrow the blues will play the browns.
5. American History (often cap.) a member of the Union army in the American Civil War or the army itself. Cf. gray (def. 13).
6. bluestocking.
7. See blue ribbon (def. 1).
8. Insects any of several blue-winged butterflies of the family Lycaenidae.
9. Printing blueline.
10. the blue:
    • the sky.
    • the sea.
    • the remote distance:
      They've vanished into the blue somewhere.
11. Idioms out of the blue, suddenly and unexpectedly:
    The inheritance came out of the blue as a stroke of good fortune.

adj. 

12. of the color of blue:
    a blue tie.
13. American History (cap.) of or pertaining to the Union army in the American Civil War.
14. (of the skin) discolored by cold, contusion, fear, or vascular collapse.
15. depressed in spirits;
    dejected;
    melancholy:
    She felt blue about not being chosen for the team.
16. holding or offering little hope;
    dismal;
    bleak:
    a blue outlook.
17. characterized by or stemming from rigid morals or religion:
    statutes that were blue and unrealistic.
18. marked by blasphemy:
    The air was blue with oaths.
19. Zoology (of an animal's pelage) grayish-blue.
20. indecent;
    somewhat obscene;
    risqué:
    a blue joke or film.
21. Idioms blue in the face, exhausted and speechless, as from excessive anger, physical strain, etc.:
    I reminded him about it till I was blue in the face.

v.t. 

22. to make blue;
    dye a blue color.
23. to tinge with bluing:
    Don't blue your clothes till the second rinse.

v.i. 

24. to become or turn blue.

• Gmc *blǣwaz; compare Old English blǣwen, contraction of blǣhǣwen deep blue, perse (see blae, hue), Old Frisian blāw, Middle Dutch blā(u), Old High German blāo (German blau), Old Norse blār
• Anglo-French blew, bl(i)u, bl(i)ef blue, livid, discolored, Old French blo, blau (French bleu)
• Middle English blewe 1250–1300

blue′ly, adv. 
blue′ness, n. 
Synonyms

• 1. azure, cerulean, sapphire.
• 15. despondent, unhappy, morose, doleful, dispirited, sad, glum, downcast.
• 16. gloomy, dispiriting.
• 17. righteous, puritanical, moral, severe, prudish.

Antonyms

• 15. happy.