(computer languages) A multiparadigm programming language focused on safety, especially safe concurrency.

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

A similar substance based on another metal.

(color) A reddish-brown color.

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

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

(intransitive) To oxidize, especially of iron or steel.

(transitive) To cause to oxidize.

(intransitive) To be affected with the parasitic fungus called rust.

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

(intransitive) Of a black cat or its fur, to turn rust-coloured following long periods of exposure to sunlight.