core

¹ American  

[kawr] / kɔr /

noun

1. the central part of a fleshy fruit, containing the seeds.

2. the central, innermost, or most essential part of anything.

   Synonyms:

   center, nub, kernel, gist, heart, essence

3. Also called magnetic core.  Electricity. the piece of iron, bundle of iron wires, or other ferrous material forming the central or inner portion in an electromagnet, induction coil, transformer, or the like.

4. (in mining, geology, etc.) a cylindrical sample of earth, mineral, or rock extracted from the ground by means of a corer so that the strata are undisturbed in the sample.

5. the inside wood of a tree.

6. Anthropology. a lump of stone, as flint, from which prehistoric humans struck flakes in order to make tools.

7. Carpentry.

   1. a thickness of wood forming a base for a veneer.

   2. a wooden construction, as in a door, forming a backing for veneers.

8. Engineering. kern.

9. Metallurgy.

   1. a thickness of base metal beneath a cladding.

   2. the softer interior of a piece of casehardened metal.

   3. a specially formed refractory object inserted into a mold to produce cavities or depressions in the casting that cannot be readily formed on the pattern.

10. Geology. the central portion of the earth, having a radius of about 2,100 miles (3,379 km) and believed to be composed mainly of iron and nickel in a molten state.

11. Also called reactor core.  Physics. the region in a reactor that contains its fissionable material.

12. Computers.

    1. Also called magnetic core.  a small ring or loop of ferromagnetic material with two states of polarization that can be changed by changing the direction of the current applied in wires wound around the ring, used to store one bit of information or to perform switching or logical functions.

    2. Also called main memory.  Also called RAM.  a term used to refer to main memory, though no longer made from from coils of ferromagnetic material.

13. Ropemaking. heart.

14. Phonetics. the final segment of a syllable beginning with the vowel and including any following consonants; the nucleus plus the coda.

15. the muscles of the torso, which provide support for the spine and pelvis.

    Building a strong core can help with posture and flexibility and can prevent back injury.

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verb (used with object)

cored, coring

1. to remove the core of (fruit).

2. to cut from the central part.

3. to remove (a cylindrical sample) from the interior, as of the earth or a tree trunk.

   to core the ocean bottom.

4. to form a cavity in (a molded object) by placing a core, as of sand, in the mold before pouring.

adjective

1. of central importance; basic; fundamental.

   the core values of our organization.

2. noting or relating to the muscles of the torso.

   core exercises for back pain.

core ² American  

[kawr, kohr] / kɔr, koʊr /

noun

Chiefly Scot.

1. a small company or group of people, especially a gang of miners or a small corps of workers.

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Core ³ American  

[kawr-ee, kohr-ee] / ˈkɔr i, ˈkoʊr i /

noun

1. Korah.

2. Classical Mythology. Kore.

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CORE ⁴ American  

[kawr, kohr] / kɔr, koʊr /

Or C.O.R.E.

noun

1. Congress of Racial Equality.

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-core ⁵ American  

1. a combining form extracted from hard-core, used to form words that name a rebellious or nonmainstream lifestyle, social movement, type of music, etc..

2. the compounding form of core, used to form words describing an aesthetic or imagery that evokes nostalgia for vintage styles, traditional skills, past trends, etc..

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-core ¹ British  

combining form

1. indicating a type of popular music

   dancecore

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combining form

1. indicating the number of processing units working in parallel in a computer

   dual-core

core ² British  

/ kɔː /

noun

1. the central part of certain fleshy fruits, such as the apple or pear, consisting of the seeds and supporting parts

2. 1. the central, innermost, or most essential part of something

      the core of the argument

   2. ( as modifier )

      the core meaning

3. a piece of magnetic material, such as soft iron, placed inside the windings of an electromagnet or transformer to intensify and direct the magnetic field

4. geology the central part of the earth, beneath the mantle, consisting mainly of iron and nickel, which has an inner solid part surrounded by an outer liquid part

5. a cylindrical sample of rock, soil, etc, obtained by the use of a hollow drill

6. shaped body of material (in metal casting usually of sand) supported inside a mould to form a cavity of predetermined shape in the finished casting

7. physics the region of a nuclear reactor in which the reaction takes place

8. a layer of wood serving as a backing for a veneer

9. computing

   1. one of several processing units working in parallel in a computer

   2. a ferrite ring formerly used in a computer memory to store one bit of information

   3. short for core store

   4. ( as modifier )

      core memory

10. archaeol a lump of stone or flint from which flakes or blades have been removed

11. physics the nucleus together with all complete electron shells of an atom

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verb

1. (tr) to remove the core from (fruit)

CORE ³ British  

/ kɔː /

acronym

1. Congress of Racial Equality

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core Scientific  

/ kôr /

1. The central or innermost portion of the Earth, lying below the mantle and probably consisting of iron and nickel. It is divided into a liquid outer core, which begins at a depth of 2,898 km (1,800 mi), and a solid inner core, which begins at a depth of 4,983 km (3,090 mi).

2. A piece of magnetizable material, such as a rod of soft iron, that is placed inside an electrical coil or transformer to intensify and provide a path for the magnetic field produced by the current running through the wire windings.

3. The central part of a nuclear reactor where atomic fission occurs. The core contains the fuel, the coolant, and the moderator.

4. A long, cylindrical sample of soil, rock, or ice collected with a drill to study the strata of material that are not visible from the surface.

5. A stone from which one or more flakes have been removed, serving as a tool in itself or as a source of flakes from which other tools could be fashioned. Stones used as cores include flint, chert, and obsidian.

6. See more at core tool

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core Cultural  

1. In geology, the central region of the Earth; it extends fourteen hundred to eighteen hundred miles from the Earth's center.

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core Idioms  

1. see rotten to the core.

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Usage

What does -core mean? The combining form -core is used like a suffix to denote "a rebellious, anti-mainstream lifestyle, social movement, type of music, etc."The form -core comes from the expression hardcore, "a form of punk rock or other nonmainstream popular music." Hardcore can denote not just a kind of a music but an entire lifestyle culture. From this, -core came to denote other music scenes, lifestyle cultures, or aesthetics.

Discover More

The core is made primarily of iron and nickel and has two parts — an inner solid core and an outer liquid core.

The mantle is the layer of the Earth that overlies the core.

Other Word Forms

• coreless adjective

Etymology

Origin of core¹

First recorded in 1350–1400; 1945–50 core ¹ for def. 11; Middle English; origin uncertain; perhaps from Old French cors “body,” from Latin corpus

Origin of core²

First recorded in 1620–30; alteration of Middle English chor(e) “group, company; choir”; chorus

Explanation

If you're looking for the most essential part or the very center of something, you're looking for its core. Like the inedible middle of an apple or your inner circle of core friends. In the late 14th century, the noun core came about from the Old French coeur, meaning “core of fruit” and more literally, “heart.” So the core of something is its very heart, whether you're talking about the seed-containing center of a fruit, the central meaning of a book, or the core courses you need to take in order to graduate.

Example Sentences

He got his patients to wear elastic bands - which simulated resistance - while doing a series of exercises that would strengthen their core.

From BBC • Apr. 14, 2026

The industry’s currency is Nielsen’s core Big Data + Panel service, which has used the Advertising Research Foundation viewership estimates since its calculations for January.

From The Wall Street Journal • Apr. 14, 2026

The 12-month increase in core prices inched up to 3.6% from 3.5%.

From MarketWatch • Apr. 14, 2026

The rationale was similar: CoreWeave has become a core part of the AI story.

From Barron's • Apr. 13, 2026

They look like the core of a fire now—bright and ancient.

From "Kwame Crashes the Underworld" by Craig Kofi Farmer

Related Words

• basis
• body
• bottom line
• crux
• essence
• focus
• foundation
• heart
• importance
• nucleus
• origin
• root
• substance
• thrust