\ ˈrəst \

Definition of rust 

(Entry 1 of 2)

1a : the reddish brittle coating formed on iron especially when chemically attacked by moist air and composed essentially of hydrated ferric oxide
b : a comparable coating produced on a metal other than iron by corrosion
c : something resembling rust : accretion
2 : corrosive or injurious influence or effect
3 : any of numerous destructive diseases of plants produced by fungi (order Uredinales) and characterized by usually reddish-brown pustular lesions also : a fungus causing this
4 : a strong reddish brown


rusted; rusting; rusts

Definition of rust (Entry 2 of 2)

intransitive verb

1 : to form rust : become oxidized iron rusts
2 : to degenerate especially from inaction, lack of use, or passage of time most men would … have allowed their faculties to rust— T. B. Macaulay
3 : to become reddish brown as if with rust the leaves slowly rusted
4 : to be affected with a rust fungus

transitive verb

1 : to cause (a metal) to form rust keep up your bright swords, for the dew will rust them— William Shakespeare
2 : to impair or corrode by or as if by time, inactivity, or deleterious use
3 : to cause to become reddish brown : turn the color of rust

Examples of rust in a Sentence


an old pump covered in rust


Your bicycle will rust if you leave it out in the rain. The moist air rusted the latch on the door. The old iron fence was rusted.
See More

Recent Examples on the Web: Noun

This use ends up generating rust and sludge, which can damage the cooling system. Zachary Palmer, Popular Mechanics, "Choosing the Right Coolant for Your Car," 4 Sep. 2018 From the Metropolitan Collection by Caesarstone, Excava blends authentic elements of rust and concrete for a one-of-a-kind look. Good Housekeeping, "Bold, Classic Style for Any Space," 14 Aug. 2018 Now ranked 156th, Murray showed both rust and shine in a 2-6, 7-6 (4), 7-5 loss to 21st-ranked Nick Kyrgios. Ben Rothenberg, New York Times, "After 342 Days, Andy Murray Returns to the Court (and Loses)," 19 June 2018 Each rust-red steel slab is inscribed with the name of a state and county, along with the names of humans lynched there and the dates they were murdered between 1877 and 1950. Julie V. Iovine, WSJ, "The Best Architecture of 2018: Building for Complex Experiences," 14 Dec. 2018 Graded to an incredibly high 62+ Rockwell hardness, these knives are also fully stain- and rust-resistant, and are precision-balanced and weighted for superior performance. Popular Mechanics, "These Precise Japanese Knives Are a Kitchen Must-Have," 11 Dec. 2018 But then the baby got adopted and raised by someone writing a love letter to Oakland in blood and rust. Sara Benincasa, Longreads, "Great Reviews Of Movies I Have Never Seen: A Reading List," 13 July 2018 There will be rust to shake off, but the hard part is over. Nick Baumgardner, Detroit Free Press, "Michigan football's Luiji Vilain is healthy, ready to compete," 15 June 2018 There are also the many notable winners who are no longer active — Bordertown, Loam, Tobacco Road, rust, Wise Monkey Orchestra, Incredible Moses Leroy and many more. George Varga,, "San Diego Music Awards will, once again, delight and frustrate attendees," 15 Mar. 2018

Recent Examples on the Web: Verb

Parts of the roof have caved in, wooden panels are missing and the kitchen stoves have rusted. Lefteris Pitarakis, Fox News, "AP PHOTOS: Istanbul's historic orphanage awaits salvation," 9 Sep. 2018 Two state troopers were handcuffing two lanky, bedraggled guys and had them leaning over the side of their rusted out Dodge Aspen, while two German shepherds sniffed the vehicle. Anne Slowey, Condé Nast Traveler, "Fear and Self-Loathing in the American Southwest," 25 July 2018 In this case, the film showcases a future that looks plenty familiar in anime and science fiction novels: a cluttered, rusted-out world that’s a little cyberpunk, a little steampunk, and a whole lot of classic anime series like Mobile Suit Gundam. Tasha Robinson, The Verge, "The Verge fall movie preview, December 2018," 7 Sep. 2018 This helps keep the bearings from pitting and the internal parts of the engine from rusting. Seth Porges, Popular Mechanics, "8 Clever Uses for Silica Gel," 29 Apr. 2010 Residents who have reddish brown water may have pipes or water heaters that are rusting. Michael Livingston,, "Water quality report offers solutions to inconvenient troubles," 11 July 2018 Sorry in advance if these vehicles depreciate in value just as quickly as that Pontiac Aztek rusting away in your driveway. Nathan Bomey, USA TODAY, "10 hot vehicles most likely to increase in value, 'terrifying the neighbors'," 22 Apr. 2018 The number of hours that have been used on it are higher than normal, and some of the areas on the frame started to rust and have become unsafe. John Benson,, "North Olmsted spending $315,000 for new Service Department vehicle purchases," 7 Mar. 2018 The truck was rusted and appeared to have been in several wrecks. Jose R. Gonzalez, Houston Chronicle, "Louisiana authorities release facial reconstruction of severed head with similarities to HPD case," 27 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'rust.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of rust


before the 12th century, in the meaning defined at sense 1a


13th century, in the meaning defined at intransitive sense 1

History and Etymology for rust


Middle English, from Old English rūst; akin to Old English rēad red — more at red

Keep scrolling for more

Learn More about rust

Statistics for rust

Last Updated

10 Jan 2019

Look-up Popularity

Time Traveler for rust

The first known use of rust was before the 12th century

See more words from the same century

Keep scrolling for more

More Definitions for rust



English Language Learners Definition of rust

 (Entry 1 of 2)

: a reddish substance that forms on iron or some other metal usually when it comes in contact with moisture or air

: a disease that causes plants to develop reddish-brown spots

: a reddish-brown color



English Language Learners Definition of rust (Entry 2 of 2)

: to form rust : to become rusty

: to cause rust to form on (something)


\ ˈrəst \

Kids Definition of rust

 (Entry 1 of 2)

1 : a reddish coating formed on metal (as iron) when it is exposed especially to moist air
2 : a plant disease caused by fungi that makes spots on plants
3 : a fungus that causes a rust


rusted; rusting

Kids Definition of rust (Entry 2 of 2)

: to make or become rusty


\ ˈrəst \

Medical Definition of rust 

1 : the reddish brittle coating formed on iron especially when chemically attacked by moist air and composed essentially of hydrated ferric oxide
2 : any of numerous destructive diseases of plants produced by fungi (order Uredinales) and characterized by reddish brown pustular lesions also : a fungus causing this

Keep scrolling for more

More from Merriam-Webster on rust

Rhyming Dictionary: Words that rhyme with rust

Spanish Central: Translation of rust

Nglish: Translation of rust for Spanish Speakers

Britannica English: Translation of rust for Arabic Speakers Encyclopedia article about rust

Comments on rust

What made you want to look up rust? Please tell us where you read or heard it (including the quote, if possible).


involving abstract or general statements

Get Word of the Day daily email!

Test Your Vocabulary

Liar, Liar Quiz

  • alt-5761dbe2ba986
  • Someone who pretends to be sick in order to avoid work is a:
True or False

Test your knowledge - and maybe learn something along the way.


Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!