rust

The deteriorated state of iron or steel as a result of moisture and oxidation.

“The rust on my bicycle chain made cycling to work very dangerous.”

A similar substance based on another metal (usually with qualification, such as "copper rust").

“aerugo. Green or blue-green copper rust; verdigris. (American Heritage Dictionary, 1973)”

A reddish-brown color.

A disease of plants caused by a reddish-brown fungus.

Damage caused to stamps and album pages by a fungal infection.

To oxidize, especially of iron or steel.

“The patio furniture had rusted in the wind-driven spray.”

To cause to oxidize.

“The wind-driven spray had thoroughly rusted the patio furniture.”

To be affected with the parasitic fungus called rust.

To (cause to) degenerate in idleness; to make or become dull or impaired by inaction.