rust

American  

[ruhst] / rʌst /

noun

• rust
  plural

1. Also called iron rust.  the red or orange coating that forms on the surface of iron when exposed to air and moisture, consisting chiefly of ferric hydroxide and ferric oxide formed by oxidation.

2. any film or coating on metal caused by oxidation.

   Synonyms:

   corrosion

3. a stain resembling this coating.

4. any growth, habit, influence, or agency tending to injure, deteriorate, or impair the mind, character, abilities, usefulness, etc.

5. Plant Pathology.

   1. any of several diseases of plants, characterized by reddish, brownish, or black pustules on the leaves, stems, etc., caused by fungi of the order Uredinales.

   2. Also called rust fungus.  a fungus causing this disease.

   3. any of several other diseases of unknown cause, characterized by reddish-brown spots or discolorations on the affected parts.

6. reddish yellow, reddish brown, or yellowish red.

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verb (used without object)

• rusts,
  present (3rd person singular)
• rusted,
  past participle,  past
• rusting
  present participle

1. to become or grow rusty, as iron.

2. to contract rust.

3. to deteriorate or become impaired, as through inaction or disuse.

   Synonyms:

   decline, decay

4. to become rust-colored.

verb (used with object)

• rusts,
  present (3rd person singular)
• rusted,
  past participle,  past
• rusting
  present participle

1. to affect with rust.

2. to impair as if with rust.

3. to make rust-colored.

adjective

1. having the color rust.

verb phrase

1. rust out (of metal pipes, machinery, etc.) to decay and become unusable through the action of rust.

2. rust together to join two metal pieces, as iron pipes, by causing the joint to rust.

3. rust through to develop holes, breaks, or the like, because of rust.

rust British  

/ rʌst /

noun

1. a reddish-brown oxide coating formed on iron or steel by the action of oxygen and moisture

2. Also called: rust fungus.  plant pathol

   1. any basidiomycetous fungus of the order Uredinales , parasitic on cereal plants, conifers, etc

   2. any of various plant diseases characterized by reddish-brown discoloration of the leaves and stem, esp that caused by the rust fungi

3. 1. a strong brown colour, sometimes with a reddish or yellowish tinge

   2. ( as adjective )

      a rust carpet

4. any corrosive or debilitating influence, esp lack of use

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verb

1. to become or cause to become coated with a layer of rust

2. to deteriorate or cause to deteriorate through some debilitating influence or lack of use

   he allowed his talent to rust over the years

rust Scientific  

/ rŭst /

1. Any of the various reddish-brown oxides of iron that form on iron and many of its alloys when they are exposed to oxygen in the presence of moisture.

2. 1. Any of various basidiomycete fungi that are parasitic on plants and produce reddish or brownish spots on leaves. Rusts attack a wide variety of plants and can cause enormous damage to crops.

   2. Any of the various plant diseases caused by these fungi.

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1. To become corroded or oxidized.

Other Word Forms

Derived Forms

• derust
  verb (used with object)
• unrust
  verb (used with object)
• rustless
  adjective

Inflected Forms

Nouns

• rust
  plural

Participles

• rusting
  present
• rusted
  past

Conjugated Forms

Present

• rust
  simple
• rusts
  simple
• have rusted
  perfect
• has rusted
  perfect
• am rusting
  progressive
• are rusting
  progressive
• is rusting
  progressive
• have been rusting
  perfect progressive
• has been rusting
  perfect progressive

Past

• rusted
  simple
• had rusted
  perfect
• was rusting
  progressive
• were rusting
  progressive
• had been rusting
  perfect progressive

Future

• will rust
  simple
• will have rusted
  perfect
• will be rusting
  progressive
• will have been rusting
  perfect progressive

Etymology

Origin of rust

before 900; (noun) Middle English; Old English rūst; cognate with German Rost; (v.) Middle English rusten, derivative of the noun; akin to red ¹

Explanation

Rust is the reddish-brown stuff that forms over time on metal that's gotten wet. Your dad's beat-up old car probably has some rust on it somewhere. If you leave your bike out overnight in the rain, it'll be fine — you can dry it off the next day. If you leave it out for several rainy weeks, though, your bike will end up with rust on it. Rust appears as brown spots where the combination of water and oxygen has coated the metal with a compound that chemists call an oxide. Rust, which is also a verb, comes from a Germanic root meaning "redness."

Example Sentences

See Examples For:

rust rusts rusted rusting

It then reverses the process, turning the rust back into iron and breathing out oxygen to charge and discharge the battery.

From The Wall Street Journal ● Aug. 12, 2026

For Joshua, it is about far more than shaking off ring rust.

From BBC ● Jul. 24, 2026

We just have to shake off a little rust first.

From Slate ● Jul. 20, 2026

The 59-year-old zoo, which occupies 133 acres in the northeast corner of Griffith Park, has struggled to maintain its national accreditation, with federal regulators finding peeling paint and rust in some exhibits.

From Los Angeles Times ● Jun. 16, 2026

I yanked on the padlock, but despite a thick encrustation of rust it seemed rock solid.

From "Miss Peregrine's Home for Peculiar Children" by Ransom Riggs

“It needs a ton of work—even plastic rusts in Key West.”

From The Wall Street Journal ● Jan. 8, 2026

The mineral cave decor — epsomite, mirabilite, sulfate — rusts into the ruddy orange of iron oxide, the deep black of manganese.

From Salon ● Oct. 7, 2023

Carbon steel rusts easily, so those knives have to be consistently washed and dried to avoid discoloration.

From Washington Times ● Jun. 9, 2023

Fungal rusts and smuts that are proliferating in our increasingly warmer and wetter world endanger the world’s coffee supply.

From Washington Post ● Jul. 15, 2022

And when the sword of the law, confided to the hands of our enemies, rusts in its sheath?

From The Sword of Honor, volumes 1 & 2 or The Foundation of the French Republic, A Tale of The French Revolution by Eug?ne Sue

But he also didn’t want to die an old man on a rusted prison cot.

From Salon ● Aug. 10, 2026

The researchers compare the damaged protein to a rusted key that no longer fits its lock.

From Science Daily ● Jul. 24, 2026

Mercantile scales and rusted bird cages are scattered across crowded shelves.

From Los Angeles Times ● Jul. 15, 2026

On a Friday afternoon, villagers flocked to the old red-brick mosque, where a rusted sign reads "established 1480".

From Barron's ● Apr. 22, 2026

There were some old rusted tools lying about and some desiccated straw lined the far left corner, but half the roof was either missing or about to fall off.

From "Summer of the Mariposas" by Guadalupe García McCall

"These coins were rusting and expanding and were capable of pressing the whole column of rock above them, pushing them up," he told BBC Radio Foyle's North West Today programme.

From BBC ● Aug. 18, 2026

The largest structure, a six-story building with dozens of broken windows, is sealed shut with rusting metal grillwork.

From The Wall Street Journal ● May 6, 2026

The reef is home to a small Philippine military outpost aboard the BRP Sierra Madre, a rusting World War Two-era ship deliberately grounded there in 1999 to assert Manila's claim to the territory.

From BBC ● Apr. 13, 2026

Electricity reverses the rusting process, allowing the iron batteries to store energy for later use.

From Barron's ● Feb. 24, 2026

The fields—wherever they were, whatever they were—had gone darker, the grass yellowing under their feet, the rides rusting, the candy apples moldering, the smell of rot and wet and damp assaulting her nostrils.

From "Bone Gap" by Laura Ruby

Related Words

• decay
• deteriorate
• wither