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
rusted; rusting; rusts
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
T. B. Macaulay3
: to become reddish brown as if with rust
the leaves slowly rusted
4
: to be affected with a rust fungus
1
: to cause (a metal) to form rust
keep up your bright swords, for the dew will rust them—William Shakespeare
William Shakespeare2
: 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
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
Stephanie Wenger, People.com, 29 Oct. 2024
The corduroy is available in the women’s NAO high-rise bootcut jean, offered in black, brown and rust and men’s AMS slim jeans in brown.
—Angela Velasquez, Sourcing Journal, 29 Oct. 2024
Mary Cornetta, Better Homes & Gardens, 29 Oct. 2024
Step 1: For pieces that are heavily rusted, start the night before by submerging your metal completely in a tub or basin of white vinegar.
—Mary Catherine McAnnally Scott, Southern Living, 15 July 2024
See all Example Sentences for rust 
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Noun
The actor wore a black suit and rust tie and O’Toole wore a coordinated look — a pantsuit with a cream blouse.
—Stephanie Wenger, People.com, 29 Oct. 2024
The corduroy is available in the women’s NAO high-rise bootcut jean, offered in black, brown and rust and men’s AMS slim jeans in brown.
—Angela Velasquez, Sourcing Journal, 29 Oct. 2024
Verb
Even if your home doesn’t have hard water or a kitchen sink made of metal (and, therefore, prone to rust), sink stains are still hard to avoid.
—Mary Cornetta, Better Homes & Gardens, 29 Oct. 2024
Step 1: For pieces that are heavily rusted, start the night before by submerging your metal completely in a tub or basin of white vinegar.
—Mary Catherine McAnnally Scott, Southern Living, 15 July 2024
See all Example Sentences for rust
Dictionary Entries Near rust
Cite this Entry
“Rust.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/rust. Accessed 28 Nov. 2024.
Copy CitationKids Definition
rust
1 of 2 noun1
: 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
noun1
: 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
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