I. ˈrəst noun
Etymology: Middle English, from Old English rūst; akin to Old English rēad red — more at red
Date: before 12th century
1.
a. : 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
II. verb
Date: 13th century
intransitive verb
1. : to form rust : become oxidized
iron rust s
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 rust ed
4. : to be affected with a rust fungus
transitive verb
1. : to cause (a metal) to form rust
keep up your bright swords, for the dew will rust them — 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