rust

noun

1.
a red or brown oxide coating on iron or steel caused by the action of oxygen and moisture
Derived from:
rust rusty
2.
a plant disease that produces a reddish-brown discoloration of leaves and stems; caused by various rust fungi
3.
the formation of reddish-brown ferric oxides on iron by low-temperature oxidation in the presence of water
Derived from:
rust
4.
any of various fungi causing rust disease in plants
5.
A strong reddish brown color.