deep

noun

1

a

: a vast or immeasurable extent : abyss

b(1)

: the extent of surrounding space or time

the azure deep

(2)

nautical : ocean

the briny deep

2

: any of the deep portions of a body of water

specifically : a generally long and narrow area in the ocean where the depth exceeds 3000 fathoms (5500 meters)

the Aldrich Deep in the south Pacific

3

: the middle or most intense part

in the deep of winter

4

nautical : any of the fathom points on a sounding line other than the marks (see mark entry 1 sense 2b)

Synonyms of deep

• midst
• middle

Examples of deep in a Sentence

the kind of cold weather that we usually have only in the deep of winter

sailors exploring the farther reaches of the briny deep

Recent Examples on the Web

Ewers followed it up by trying to squeeze another pass into a tight window deep, but overthrew his target high for an incompletion. —David Furones, Sun Sentinel, 27 May 2026

Architectonics takes this murky style and plunges it to a new deep, incorporating the bronze gong and chime sounds of gamelan while burying his rhythms in dense, dubby layers of incense smoke. —Sam Goldner, Pitchfork, 13 Apr. 2026

Ankle-deep, knee-deep, waist-deep. —Literary Hub, 26 Feb. 2026

The two-deep should be bolstered by the Luniewski twins, who will challenge to start, along with Lawrence, Montgomery and Jones, among others. —Kirk Kenney, San Diego Union-Tribune, 7 Feb. 2026

Word History

Etymology

First Known Use

before the 12th century, in the meaning defined at sense 1b(2)

Phrases Containing deep

• between the devil and the deep blue sea
• deep cut
• deep-dish
• deep dive
• deep down
• deep ecology
• deep fat
• deep-fat fryer
• deep focus
• deep freeze
• deep-fry
• deep fryer
• deep in debt
• deep learning
• deep pocket
• deep-rooted
• deep-sea
• deep-seated
• deep six
• deep-sky
• deep space
• deep state
• deep structure
• deep temporal artery
• deep throat
• deep web
• go off the deep end
• in deep doo-doo
• in deep water
• in (too) deep
• jump in (at) the deep end
• knee-deep
• neck-deep
• rapture of the deep
• run deep
• skin-deep
• still waters run deep
• take a deep breath
• the deep
• the deep end
• the deep of the night
• throw in (at) the deep end

Rhymes for deep

• beep
• cheap
• creep
• heap
• jeep
• keep
• leap
• peep
• reap
• seep
• sheep
• sleep

Kids Definition

deep

1 of 3 adjective

ˈdēp 

1

a

: extending far downward

a deep well

b

: having a great distance between the top and bottom surfaces : not shallow

deep water

c

: extending well inward from an outer or front surface

a deep gash

d

: extending far outward from a center

deep space

e

: occurring or located near the outer limits

deep right field

2

: having a specified extension downward or backward

a shelf 40 centimeters deep

3

a

: difficult to understand

a deep book

b

: mysterious, obscure

a deep dark secret

c

: profound sense 1

a deep thinker

d

: completely absorbed

deep in thought

e

: being to an extreme degree : heavy

deep sleep

4

a

: dark and rich in color

a deep red

b

: having a low musical pitch or range

a deep voice

5

a

: coming from or located well within

a deep sigh

a house deep in the forest

b

: covered, enclosed, or filled often to a specified degree

knee-deep in water

a road deep with snow

deeply adverb

deep

2 of 3 adverb

1

: to a great depth : deeply

2

: far on : late

read deep into the night

3

: near the outer limits

the shortstop was playing deep

deep

3 of 3 noun

1

a

: an extremely deep place or part (as of the ocean)

b

: ocean sense 1

2

: the middle or most intense part

the deep of night

Medical Definition

deep

adjective

ˈdēp 

1

a

: extending well inward from an outer surface

a deep gash

b(1)

: not located superficially within the body or one of its parts

deep pressure receptors in muscles

(2)

: resulting from or involving stimulation of deep structures

deep pain

deep reflexes

2

: being below the level of the conscious

deep neuroses

deeply adverb