Dictionary

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

Example: 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").

Example: 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.

To oxidize, especially of iron or steel.

Example: The patio furniture had rusted in the wind-driven spray.

To cause to oxidize.

Example: 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.