deep

American  

[deep] / dip /

adjective

deeper, deepest

1. extending far down from the top or surface.

   a deep well;

   a deep valley.

   Antonyms:

   shallow

2. extending far in or back from the front or from an edge, surface, opening, etc., considered as the front.

   a deep shelf.

3. extending far in width; broad.

   deep lace;

   a deep border.

4. ranging far from the earth and sun.

   a deep space probe.

5. having a specified dimension in depth.

   a tank 8 feet deep.

6. covered or immersed to a specified depth (often used in combination).

   standing knee-deep in water.

7. having a specified width or number of items from front to back (often used in combination).

   shelves that are 10 inches deep;

   cars lined up at the entrance gates three-deep.

8. extending or cutting far down relative to the surface of a given object.

   The knife made a deep scar in the table.

9. situated far down, in, or back.

   deep below the surface;

   deep in the woods.

10. reaching or advancing far down.

    a deep dive.

    Antonyms:

    shallow

11. coming from far down.

    a deep breath.

12. made with the body bent or lowered to a considerable degree.

    a deep bow.

13. immersed or submerged in or heavily covered with (followed byin ).

    a road deep in mud.

14. difficult to penetrate or understand; abstruse.

    a deep allegory.

    Synonyms:

    obscure, mysterious, recondite

15. not superficial; profound.

    deep thoughts.

16. grave or serious.

    deep disgrace.

17. heartfelt; sincere.

    deep affections.

18. absorbing; engrossing.

    deep study.

19. great in measure; intense; extreme.

    deep sorrow.

20. sound and heavy.

    deep sleep.

21. (of colors) dark and vivid.

    a deep red.

22. low in pitch, as sound, a voice, or the like.

    deep, sonorous tones.

23. having penetrating intellectual powers.

    a deep scholar.

    Synonyms:

    sagacious, shrewd, intelligent, wise

24. profoundly cunning or artful.

    a deep and crafty scheme.

25. mysterious; obscure.

    deep, dark secrets.

26. immersed or involved; enveloped.

    a man deep in debt.

27. absorbed; engrossed.

    deep in thought.

28. Baseball. relatively far from home plate.

    He hit the ball into deep center field.

29. Linguistics. belonging to an early stage in the transformational derivation of a sentence; belonging to the deep structure.

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noun

1. the deep part of a body of water, especially an area of the ocean floor having a depth greater than 18,000 feet (5,400 meters).

2. a vast extent, as of space or time.

3. the part of greatest intensity, as of winter.

4. Nautical. any of the unmarked levels, one fathom apart, on a deep-sea lead line.

5. Chiefly Literary. the deep, the sea or ocean.

   He was laid to rest in the deep.

adverb

deeper, deepest

1. to or at a considerable or specified depth.

   The boat rode deep in the water.

2. far on in time.

   He claimed he could see deep into the future.

3. profoundly; intensely.

4. Baseball. at or to a deep place or position.

   The outfielders played deep, knowing the batter's reputation as a slugger.

idioms

1. in deep,

   1. inextricably involved.

   2. having made or committed oneself to make a large financial investment.

2. go off the deep end,

   1. to enter upon a course of action with heedless or irresponsible indifference to consequences.

   2. to become emotionally overwrought.

3. in deep water,

   1. in difficult or serious circumstances; in trouble.

   2. in a situation beyond the range of one's capability or skill.

      You're a good student, but you'll be in deep water in medical school.

deep British  

/ diːp /

adjective

1. extending or situated relatively far down from a surface

   a deep pool

2. extending or situated relatively far inwards, backwards, or sideways

   a deep border of trees

3. cricket relatively far from the pitch

   the deep field

   deep third man

4. 1. (postpositive) of a specified dimension downwards, inwards, or backwards

      six feet deep

   2. ( in combination )

      a six-foot-deep trench

5. coming from or penetrating to a great depth

   a deep breath

6. difficult to understand or penetrate; abstruse

7. learned or intellectually demanding

   a deep discussion

8. of great intensity; extreme

   deep happiness

   deep trouble

9. absorbed or enveloped (by); engrossed or immersed (in)

   deep in study

   deep in debt

10. very cunning or crafty; devious

    a deep plot

11. mysterious or obscure

    a deep secret

12. (of a colour) having an intense or dark hue

13. low in pitch or tone

    a deep voice

14. informal

    1. to lose one's temper; react angrily

    2. to act rashly

15. in a tricky position or in trouble

16. See end 1

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noun

1. any deep place on land or under water, esp below 6000 metres (3000 fathoms)

2. 1. a poetic term for the ocean

   2. cricket the area of the field relatively far from the pitch

3. the most profound, intense, or central part

   the deep of winter

4. a vast extent, as of space or time

5. nautical one of the intervals on a sounding lead, one fathom apart

adverb

1. far on in time; late

   they worked deep into the night

2. profoundly or intensely

3. informal in reality, esp as opposed to appearance

   she is a very kind person deep down

4. long ago

deep More Idioms  

More idioms and phrases containing deep

• beauty is only skin deep
• between a rock and a hard place (devil and deep blue sea)
• go off the deep end
• in deep
• still waters run deep

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Other Word Forms

• deeply
  adverb
• deepness
  noun
• nondeep
  adjective
• overdeep
  adjective
• undeep
  adjective
• undeeply
  adverb

Etymology

Origin of deep

First recorded before 900; Middle English dep, Old English dēop; akin to Gothic diups, Old Norse djupr, Dutch diep, Old High German tiof; akin to dip ¹ ( def. ), dive ( def. )

Explanation

How deep a body of water is can be measured from the surface of water to the bottom. You should always be sure you know how deep a swimming pool is before demonstrating your backward somersault dive. Water can be deep or shallow, and exactly how deep it is can be measured. You can also describe a space not made of water as deep — like when you discover a little house made of candy deep, or far, in the woods. Things can even be figuratively deep when they are extreme, like "deep thoughts" or a "deep recession." The Old English word deop means "deep," but it also means, "awful, mysterious, and solemn."

Example Sentences

Polk has spent decades studying this type of propulsion, contributing to earlier missions such as Dawn and Deep Space 1, which demonstrated electric propulsion beyond Earth orbit for the first time.

From Science Daily • May 6, 2026

This story was produced in partnership with Deep South Today, a network of nonprofit, nonpartisan local newsrooms in Louisiana and Mississippi.

From Slate • May 5, 2026

Deep in the heart of the Delta lies Clarksdale, Miss., widely known as the birthplace of the blues.

From Los Angeles Times • May 1, 2026

A youthful, digital version of Kilmer appeared in the trailer for archeological action pic "As Deep as the Grave," telling another character: "Don't fear the dead and don't fear me."

From Barron's • May 1, 2026

It was taboo because it exposed the inherent contradictions of the Virginia position, which was much closer to the position of the Deep South than Madison wished to acknowledge, even to himself.

From "Founding Brothers: The Revolutionary Generation" by Joseph J. Ellis

Related Words

• dark
• extreme
• great
• hard
• profound
• rich
• strong
• vivid