rust

Short definition from Wiktionary

Noun

1. 1
   The deteriorated state of iron or steel as a result of moisture and oxidation; it consists mostly of iron(III) oxide (ferric oxide) and iron(II) oxide (ferrous oxide).
2. 2
   A similar substance based on another metal.
3. 3
   A reddish-brown color.
4. 4
   A disease of plants caused by a reddish-brown fungus.
5. 5
   Damage caused to stamps and album pages by a fungal infection.

Verb

1. 1
   To oxidize, especially of iron or steel.
2. 2
   To cause to oxidize.
3. 3
   To be affected with the parasitic fungus called rust.
4. 4
   To (cause to) degenerate in idleness; to make or become dull or impaired by inaction.
5. 5
   Of a black cat or its fur, to turn rust-coloured following long periods of exposure to sunlight.

Proper noun

1. 1
   A surname.
2. 2
   A multiparadigm programming language focused on safety, especially safe concurrency.