The Collaborative International Dictionary
Rust \Rust\, n. [AS. rust; akin to D. roest, G. & Sw. rost, Icel. ry[eth]; -- named from its color, and akin to E. red.
(Chem.) The reddish yellow coating formed on iron when exposed to moist air, consisting of ferric oxide or hydroxide; hence, by extension, any metallic film of corrosion.
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(Bot.) A minute mold or fungus forming reddish or rusty spots on the leaves and stems of cereal and other grasses ( Trichobasis Rubigo-vera), now usually believed to be a form or condition of the corn mildew ( Puccinia graminis). As rust, it has solitary reddish spores; as corn mildew, the spores are double and blackish.
Note: Rust is also applied to many other minute fungi which infest vegetation, such as the species of Ustilago, Uredo, and Lecythea.
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That which resembles rust in appearance or effects. Specifically:
A composition used in making a rust joint. See Rust joint, below.
Foul matter arising from degeneration; as, rust on salted meat.
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Corrosive or injurious accretion or influence.
Sacred truths cleared from all rust and dross of human mixtures.
--Eikon Basilike.Note: Rust is used in the formation of compounds of obvious meaning; as, rust-colored, rust-consumed, rust-eaten, and the like.
Rust joint, a joint made between surfaces of iron by filling the space between them with a wet mixture of cast-iron borings, sal ammoniac, and sulphur, which by oxidation becomes hard, and impervious to steam, water, etc.
Rust mite (Zo["o]l.), a minute mite ( Phytopius oleivorus) which, by puncturing the rind, causes the rust-colored patches on oranges.