Definition of: rust

(rust) noun
1. The reddish or yellow coating caused on iron and steel by oxidation, as by the action of air and moisture, consisting of ferric hydroxide, Fe(OH)₃, and ferric oxide, Fe₂O₃.
2. A film of oxide formed on any metal by corrosion.
3. Any of the parasitic fungi of the order Uredinales, living on the tissues of higher plants.
4. The diseases caused by such fungi; incorrectly, any one of several diseases not caused by these fungi.
5. Any coating or accretion formed by a corrosive or degenerative process: rust on salted meat.
6. A condition, affection, or tendency that destroys or weakens energy or active qualities: the rust of idleness.
7. Any of several shades of reddish–brown, somewhat like the color of rust, but containing more orange.
—v.t. & v.i.
1. To become or cause to become rusty; undergo or cause to undergo oxidation.
2. To contract or cause to contract rust.
3. To become or cause to become weakened or impaired because of inactivity or disuse: to allow one's powers to rust.
4. To make or become rust–colored. [OE]