rust

1 of 2

noun

ˈrəst 

1

a

: 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

rust

2 of 2

verb

rusted; rusting; rusts

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

Years of storage in the damp basement rusted the tools.

3

: to cause to become reddish brown : turn the color of rust

Examples of rust in a Sentence

Noun

an old pump covered in rust

Verb

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.

Recent Examples on the Web

Noun

Corrosion warranty Corrosion warranties protect against rust on the body of your vehicle. —Alora Bopray, USA Today, 5 Dec. 2025

Special attention was paid in ensuring this would in no way impact its overall functionality—in other words, rust wouldn’t sacrifice its structural integrity—and subtle aftermarket additions were added to bolster its appeal, as well as accommodate its contemporary componentry. —Peter Nelson, Robb Report, 3 Dec. 2025

Verb

Not to mention, tools that have rusted can become dangerous and need to be tossed immediately for safety precautions. —Ashlyn Needham, Southern Living, 3 Dec. 2025

Moisture can rust internal wiring and cause devices to short circuit, ruining them. —Mary Cornetta, Better Homes & Gardens, 29 Nov. 2025

Word History

Etymology

Noun

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

First Known Use

Noun

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

Verb

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

Phrases Containing rust

• anti-rust
• blister rust
• cedar-apple rust
• crown rust
• leaf rust
• red rust
• rust belt
• rust bucket
• rust mite
• stem rust
• wheat rust
• white-pine blister rust
• white rust

Rhymes for rust

• bused
• bust
• crust
• cussed
• dust
• fussed
• fust
• gust
• just
• lust
• mussed
• must

Kids Definition

rust

1 of 2 noun

ˈrəst 

1

: a reddish brittle coating formed on iron especially when chemically attacked by moist air and composed chiefly of ferric oxide

2

a

: any of numerous destructive diseases of plants caused by fungi and characterized by reddish brown spots

b

: any of an order of fungi that cause plant rusts

3

: a reddish brown

rust

2 of 2 verb

: to form or cause to form rust

iron rusts

Medical Definition

rust

noun

ˈrəst 

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 Pucciniales) and characterized by reddish brown pustular lesions

also : a fungus causing this