blue

1 of 3

adjective

ˈblü 

bluer; bluest

1

: of the color whose hue is that of the clear sky : of the color blue (see blue entry 2 sense 1)

a blue jacket

her bright blue eyes

The house is blue with white shutters.

2

a

: bluish

the blue haze of tobacco smoke

b

: discolored by or as if by bruising

blue with cold

c

: bluish gray

a blue cat

3

a

: low in spirits : melancholy

has been feeling blue

b

: marked by low spirits : depressing

a blue funk

things looked blue

4

: wearing blue

the blue team

5

of a woman : learned, intellectual

… the ladies were very blue and well-informed …

—William Thackeray

6

: puritanical

… a blue Sunday city …

—James Street

7

a

: profane, indecent

a blue movie

b

: off-color, risqué

blue jokes

8

music : of, relating to, or used in blues (see blues sense 3)

a blue song

9

US politics : tending to support Democratic candidates or policies

As has become increasingly clear over the past few general elections, with their red states and blue states, an American Presidential campaign is no longer truly national.

—Hendrik Hertzberg

compare purple sense 3, red sense 5

bluely adverb

blueness noun

see also:

blue in the face

blue

2 of 3

noun

plural blues

1

: a color whose hue is that of the clear sky or that of the portion of the color spectrum lying between green and violet

Blue is his favorite color.

shades of blue

2

a

: a pigment or dye that colors blue

b

: bluing

adding blue to the laundry

3

a

: blue clothing or cloth

will be wearing blue

b

blues plural : a blue costume or uniform

wearing their dress blues

4

a

: a Union soldier in the American Civil War

b

often Blue : the Union army

the Blue versus the Gray

5

a(1)

: sky

(2)

: the far distance

disappeared into the blue

b

: sea

6

: a blue object

the horse that won the blue [=blue ribbon]

… is bartered … like a stack of blues [=blue chips] in a Reno casino.

—John Lewis

7

: bluestocking

praised the writings of her fellow blues

8

biology : any of numerous small chiefly blue butterflies (family Lycaenidae)

9

: bluefish

fishing for blues

10

: blue cheese

11

physics : one of the three colors (see color entry 1 sense 15) that quarks have in the theory of quantum chromodynamics

One cannot have a single quark on its own because it would have a color (red, green, or blue). Instead, a red quark has to be joined to a green and a blue quark by a "string" of gluons (red + green + blue = white). Such a triplet constitutes a proton or a neutron.

—Stephen Hawking

see also:

out of the blue

blue

3 of 3

verb

blued; blueing or bluing; blues

transitive verb

: to make (something) blue in color: such as

a

: to dye, tint, or paint (something) blue

Last, the generation of the grandmothers, in immaculately blued hair …

—John Updike

Tattoos blued his upper arms.

—Jerry Spinelli

b

: to heat (iron or steel) to about 550 to 600°F (288 to 316°C) so that it acquires a bluish protective coating

the blued barrel of the gun

Between banks shrouded with snow, the river gleamed darkly, like blued steel with gold chips of sunlight dancing on each riffle.

—Pete Bodo

intransitive verb

: to turn blue

their blueing fingers

see also:

blue the air

Synonyms of blue

Adjective

• pornographic
• obscene
• vulgar
• dirty
• nasty
• foul
• filthy
• suggestive
• gross

Noun

• sky

Examples of blue in a Sentence

Adjective

was shocked at the blue banter on that satellite-radio talk show

a cold, dreary day always leaves me blue

Noun

Her favorite color is blue.

a mixture of blues and greens

They sailed off into the blue.

Recent Examples on the Web

Adjective

There’s an update on the barn jacket in a soft light blue wash, with a contrast white leather collar; a sweeping denim car coat ideal for transitional weather, and an A-line denim skirt designed to be worn over pants. —Libby Page, Vogue, 6 Mar. 2026

The gray, white, and blue stripes, accented with an intermittent chevron pattern, add interest, while moderate distressing helps disguise everyday wear and tear. —Shea Simmons, Southern Living, 6 Mar. 2026

Noun

Shop it in this earthy olive green hue with 60 percent off, or opt for a variety of colors from black to clay, brown, maple, and light denim blue. —Caley Sturgill, Southern Living, 8 Mar. 2026

Spring break calls for sand, sun, and surf, an escape from the midwinter blues. —Evie Carrick, Travel + Leisure, 7 Mar. 2026

Word History

Etymology

Adjective, Noun, and Verb

Middle English, from Anglo-French blef, blew, of Germanic origin; akin to Old High German blāo blue; akin to Latin flavus yellow

First Known Use

Adjective

13th century, in the meaning defined at sense 1

Noun

14th century, in the meaning defined at sense 1

Verb

1606, in the meaning defined at transitive sense

Phrases Containing blue

• baby blue
• baby blue eyes
• between the devil and the deep blue sea
• black-and-blue
• blue agave
• blue baby
• blue blood
• blue book
• blue catfish
• blue cheese
• blue chip
• blue-chipper
• blue cohosh
• blue-collar
• blue corn
• blue crab
• blue curls
• blue devils
• blue-eyed
• blue-eyed grass
• blue flag
• blue flag iris
• blue flu
• blue from the cold
• blue grama
• blue-green alga
• blue gum
• blue heeler
• blue heron
• blue in the face
• blue jay
• blue jeans
• blue law
• blue line
• blue marlin
• blue mold
• blue moon
• blue mussel
• blue note
• blue-pencil
• blue pike
• blue plate
• blue point
• blue racer
• blue riband
• blue-ribbon
• blue screen
• blue screen of death
• blue shark
• blue sheep
• blue-sky
• blue-sky law
• blue spruce
• blue streak
• blue tang
• blue the air
• blue vitriol
• blue water
• blue whale
• blue-winged teal
• blue with cold
• blue zone
• bolt from the blue
• bolt out of the blue
• bromothymol blue
• bromthymol blue
• cobalt blue
• Colorado blue spruce
• cornflower blue
• go blue
• great blue heron
• Kerry blue terrier
• methylene blue
• midnight blue
• navy blue
• once in a blue moon
• out of the blue
• peacock blue
• powder blue
• Prussian blue
• royal blue
• Russian blue
• scream blue murder
• sky blue
• slate blue
• steel blue
• talk a blue streak
• teal blue
• the blue
• toluidine blue
• true-blue
• turquoise blue

Rhymes for blue

• blew
• boo
• brew
• chew
• chou
• clue
• coo
• coup
• crew
• cue
• dew
• do

Kids Definition

blue

1 of 3 adjective

ˈblü 

1

: of the color blue

2

: low in spirits : melancholy

3

: tending to support Democratic policies or candidates

blue states

blueness noun

blue

2 of 3 noun

1

: the color of the clear daytime sky or of the colors of light between green and violet

2

: blue clothing or cloth

3

a

: sky sense 1

b

: sea sense 1a

blue

3 of 3 verb

blued; blueing or bluing

: to make or turn blue

Medical Definition

blue

1 of 2 adjective

ˈblü 

bluer; bluest

: of the color blue

blue

2 of 2 noun

1

: a color whose hue is that of the clear sky or that of the portion of the color spectrum lying between green and violet

2

: a pigment or dye that colors blue see prussian blue