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English definition of “rust”

rust

noun [U]  /rʌst/ us  
a red-brown substance that forms on the surface of iron and steel as a result of decay caused by reacting with air and water
rust
verb [I/T]  /rʌst/ us  
[I] Stainless steel won’t rust.
(Definition of rust from the Cambridge Academic Content Dictionary © Cambridge University Press)
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