Rusts meaning : The deteriorated state of iron or steel as a result of moisture and oxidation. A similar substance based on another metal (usually with qualification, such as "copper rust"). 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. To cause to oxidize. To be affected with the parasitic fungus called rust. To (cause to) degenerate in idleness; to make or become dull or impaired by inaction.