Source : Webster's Revised Unabridged Dictionary (1913)

Rust \Rust\, v. i. [imp. & p. p. {Rusted}; p. pr. & vb. n.
   {Rusting}.] [AS. rustian.]
   1. To contract rust; to be or become oxidized.

            If gold ruste, what shall iron do?    --Chaucer.

            Our armors now may rust.              --Dryden.

   2. To be affected with the parasitic fungus called rust;
      also, to acquire a rusty appearance. as plants.

   3. Fig.: To degenerate in idleness; to become dull or
      impaired by inaction.

            Must I rust in Egypt? never more Appear in arms, and
            be the chief of Greece?               --Dryden.

Rust \Rust\, n. [AS. rust; akin to D. roest, G. & Sw. rost,
   Icel. ry[eth]; -- named from its color, and akin to E. red.
   [root]113. See {Red}.]
   1. (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.

   2. (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}.

   3. That which resembles rust in appearance or effects.
      Specifically: (a) A composition used in making a rust
      joint. See {Rust joint}, below.
      (b) Foul matter arising from degeneration; as, rust on
          salted meat.
      (c) 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.

Rust \Rust\, v. t.
   1. To cause to contract rust; to corrode with rust; to affect
      with rust of any kind.

            Keep up your bright swords, for the dew will rust
            them.                                 --Shak.

   2. Fig.: To impair by time and inactivity. --Johnson.

Source : WordNet®

rust
     adj : of the color of rust [syn: {rusty}]

rust
     v 1: become destroyed by water, air, or an etching chemical such
          as an acid; "The metal corroded"; "The pipes rusted"
          [syn: {corrode}]
     2: cause to deteriorate due to the action of water, air, or an
        acid; "The acid corroded the metal"; "The steady dripping
        of water rusted the metal stopper in the sink" [syn: {corrode},
         {eat}]
     3: become coated with oxide

rust
     n 1: a red or brown oxide coating on iron or steel caused by the
          action of oxygen and moisture
     2: a reddish-brown discoloration of leaves and stems caused by
        a rust fungus
     3: the formation of reddish-brown ferric oxides on iron by
        low-temperature oxidation in the presence of water [syn: {rusting}]
     4: any of various fungi causing rust disease in plants [syn: {rust
        fungus}]