to rust or become rusty, specifically referring to the oxidation of metal

to rust away

to prevent rust; to resist rusting

rusty or discolored spots on plants, typically caused by fungal infection

tea stain (on the inside of a teapot, cup, etc.)

rust-resistant iron (an informal term for certain nickel-free stainless steels, usually of lower quality and less corrosion-resistant than true stainless steel such as 304 or 316)

a blade will get rusty if it is not sharpened; a man will fall behind if he doesn't study

(bird species of China) rusty-flanked treecreeper (Certhia nipalensis)

(bird species of China) slaty-backed flycatcher (Ficedula erithacus)

(bird species of China) rusty-cheeked scimitar babbler (Erythrogenys erythrogenys)

bird species of China: rusty-bellied shortwing (Brachypteryx hyperythra)

Rust Belt

(bird species of China) rusty-fronted barwing (Actinodura egertoni)

a "screw that never rusts" – metaphor used in CCP propaganda to praise loyal, selfless contributors, famously applied to model worker Lei Feng