Definition of rust
(Entry 1 of 2)
1a : the reddish brittle coating formed on iron especially when chemically attacked by moist air and composed essentially of hydrated ferric oxide
b : a comparable coating produced on a metal other than iron by corrosion
c : something resembling rust : accretion
2 : corrosive or injurious influence or effect
3 : any of numerous destructive diseases of plants produced by fungi (order Uredinales) and characterized by usually reddish-brown pustular lesions also : a fungus causing this
4 : a strong reddish brown
rust
verbrusted; rusting; rusts
Definition of rust (Entry 2 of 2)
1 : to form rust : become oxidized
iron rusts
2 : to degenerate especially from inaction, lack of use, or passage of time
most men would … have allowed their faculties to rust— T. B. Macaulay
3 : to become reddish brown as if with rust
the leaves slowly rusted
4 : to be affected with a rust fungus
1 : to cause (a metal) to form rust
keep up your bright swords, for the dew will rust them— William Shakespeare
2 : to impair or corrode by or as if by time, inactivity, or deleterious use
3 : to cause to become reddish brown : turn the color of rust
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The first known use of rust was before the 12th century
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