crust

American  

[kruhst] / krʌst /

noun

• crusts
  plural

1. the brown, hard outer portion or surface of a loaf or slice of bread (distinguished from crumb).

2. a slice of bread from the end of a loaf, consisting chiefly of this.

3. the pastry covering the outside of a pie or other dish.

4. a piece of stale bread.

5. any more or less hard external covering or coating.

   a crust of snow.

6. Geology. the outer layer of the earth, about 22 miles (35 km) deep under the continents continental crust and 6 miles (10 km) deep under the oceans oceanic crust.

7. a scab or eschar.

8. Slang. unabashed self-assertiveness; nerve; gall.

   He had a lot of crust going to the party without an invitation.

9. deposit from wine, as it ripens during aging, on the interior of bottles, consisting of tartar and coloring matter.

10. the hard outer shell or covering of an animal.

11. Australian Slang. a living or livelihood.

    What do you do for a crust?

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verb (used with object)

• crusts,
  present (3rd person singular)
• crusted,
  past participle,  past
• crusting
  present participle

1. to cover with or as with a crust; encrust.

2. to form (something) into a crust.

verb (used without object)

• crusts,
  present (3rd person singular)
• crusted,
  past participle,  past
• crusting
  present participle

1. to form or contract a crust.

2. to form into a crust.

crust British  

/ krʌst /

noun

1. 1. the hard outer part of bread

   2. a piece of bread consisting mainly of this

2. the baked shell of a pie, tart, etc

3. any hard or stiff outer covering or surface

   a crust of ice

4. the solid outer shell of the earth, with an average thickness of 30–35 km in continental regions and 5 km beneath the oceans, forming the upper part of the lithosphere and lying immediately above the mantle, from which it is separated by the Mohorovičić discontinuity See also sial sima

5. the dry covering of a skin sore or lesion; scab

6. a layer of acid potassium tartrate deposited by some wine, esp port, on the inside of the bottle

7. the hard outer layer of such organisms as lichens and crustaceans

8. slang impertinence

9. slang a living (esp in the phrase earn a crust )

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verb

1. to cover with or acquire a crust

2. to form or be formed into a crust

crust Scientific  

/ krŭst /

1. The solid, outermost layer of the Earth, lying above the mantle.

2. ◆ The crust that includes continents is called continental crust and is about 35.4 to 70 km (22 to 43.4 mi) thick. It consists mostly of rocks, such as granites and granodiorites, that are rich in silica and aluminum, with minor amounts of iron, magnesium, calcium, sodium, and potassium.

3. ◆ The crust that includes ocean floors is called oceanic crust and is about 4.8 to 9.7 km (3 to 6 mi) thick. It has a similar composition to that of continental crust, but has higher concentrations of iron, magnesium, and calcium and is denser than continental crust. The predominant type of rock in oceanic crust is basalt.

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crust Cultural  

1. In geology, the outermost layer of the Earth. It overlies the mantle.

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crust Idioms  

1. see upper crust.

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Discover More

The crust includes the continents and the ocean bottom and is generally estimated to be about five to twenty-five miles thick.

The crust is made from relatively lightweight rocks that floated to the surface when the Earth was molten early in its history.

Other Word Forms

Derived Forms

• undercrust
  noun
• intercrust
  verb (used with object)
• crustless
  adjective

Inflected Forms

Nouns

• crusts
  plural

Participles

• crusting
  present
• crusted
  past

Conjugated Forms

Present

• crust
  simple
• crusts
  simple
• have crusted
  perfect
• has crusted
  perfect
• am crusting
  progressive
• are crusting
  progressive
• is crusting
  progressive
• have been crusting
  perfect progressive
• has been crusting
  perfect progressive

Past

• crusted
  simple
• had crusted
  perfect
• was crusting
  progressive
• were crusting
  progressive
• had been crusting
  perfect progressive

Future

• will crust
  simple
• will have crusted
  perfect
• will be crusting
  progressive
• will have been crusting
  perfect progressive

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Etymology

Origin of crust

First recorded in 1275–1325; Middle English, from Anglo-French, Old French cruste, croste, from Latin crusta “hard coating, crust”

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Explanation

The crust is a hard layer that forms on the outside of something, like a loaf of bread. Little kids often like their sandwiches with the crust cut off. You’ve probably eaten lots of crusts — bread crust, pie crust — any food that’s hard on the outside and soft on the inside has a crust. Crust is also a verb meaning “to form a hard outer layer.” Crusting happens with more than just food, like when a layer of dirt crusts your clothes after a romp in the mud. The Earth has a hard crust too. Little kids don’t like to eat that either, usually.

Example Sentences

See Examples For:

crust crusts crusted crusting

Wildfires can make soils become hydrophobic, with vaporized organic matter forming a waxy crust that repels water.

From Los Angeles Times ● Oct. 22, 2026

The survey begat headlines in the media, especially in finance-oriented publications like Fortune and Barron’s, that figuratively wrung their hands over the travails of the upper crust.

From Los Angeles Times ● Oct. 20, 2026

Proposed explanations have included differences in how the Moon's original magma ocean circulated, a massive collision, heating caused by gravitational tides, and uneven development of the lunar crust.

From Science Daily ● Oct. 14, 2026

As these continental fragments came together, immense pressure and heat reshaped large sections of Earth's crust.

From Science Daily ● Oct. 11, 2026

Sam nibbled out the rest of the good part of his sandwich and arranged the crust in an on his plate.

From "All About Sam" by Lois Lowry

In one session, Sylvia mentioned: “On the weekends, I usually just make a meal out of the bread crusts I cut off my kids’ sandwiches.

From Slate ● Sep. 23, 2026

Crusted scabies, previously known as Norwegian scabies, causes a "scaly rash and thickened crusts of skin", external containing thousands of mites, and can be due to reduced immunity, although that is not always the case.

From BBC ● Jul. 10, 2026

Still, executives expressed optimism during the earnings call about things like Totino’s pizza crusts and seasoned pizza rolls, as well as Asian- and Mexican-inspired snacks.

From MarketWatch ● Jul. 1, 2026

Maybe it’s homemade peanut butter and jelly sandwiches made on pillowy Wonder Bread, with the crusts cut off.

From Salon ● Jun. 28, 2026

Sinks everywhere are clogged with scraps of lettuce, decomposing lemon wedges, water-logged toast crusts.

From "Nickel and Dimed: On (Not) Getting By in America" by Barbara Ehrenreich

However, many dogs were found with "matted and crusted coats" that required treatment.

From BBC ● Apr. 9, 2026

Anything that’s old, spoiled, crusted over, or vaguely suspect can go — no second-guessing required.

From Salon ● Mar. 19, 2026

Constable’s famously crusted, white-flecked surfaces, as seen in this painting’s coarsely textured beams and choppy canal water, and in its windswept, cloud-filled skies, became touchstones in his work.

From The Wall Street Journal ● Feb. 4, 2026

I’ve tried lots of gardening gloves, but they all had the same problem: I had to peel them off to use my smartphone, which isn’t easy when they’re wet or crusted with dirt.

From Los Angeles Times ● Nov. 3, 2024

Our sleep shirts crusted over during the night, drying and hardening with the hot air and dust like they had been lightly starched, the way Grandma did the collars of my dad’s dress shirts.

From "The Miseducation of Cameron Post" by emily m. danforth

The spots fill up with fluid and become blisters before crusting over to form scabs, which eventually drop off and clear up.

From BBC ● Aug. 28, 2025

Two days later the reaction arrived: redness, itching, oozing, crusting and small, fluid-filled blisters up and down his legs.

From Los Angeles Times ● Apr. 5, 2025

In “Downton” Fellowes wrote all the best set-ups and punchlines for Violet, inspired by Smith’s near-flawless track record with crusting each phrase with the perfect sear.

From Salon ● Oct. 1, 2024

But not just any rust stain: This one had really hit its mature stride, crusting corroded metal onto the unsealed paver surface — sort of like iron-oxide barnacles.

From Seattle Times ● Sep. 29, 2022

A slick of ice spread from the places the Sleeper had stepped, crusting everything in his wake.

From "Aru Shah and the End of Time" by Roshani Chokshi

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Related Words

• layer
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