Definition of "Rust" :

noun: any of various fungi causing rust disease in plants

noun: the formation of reddish-brown ferric oxides on iron by low-temperature oxidation in the presence of water

noun: a plant disease that produces a reddish-brown discoloration of leaves and stems; caused by various rust fungi

noun: a red or brown oxide coating on iron or steel caused by the action of oxygen and moisture

verb: become coated with oxide

verb: become destroyed by water, air, or a corrosive such as an acid

"The pipes rusted."

verb: cause to deteriorate due to the action of water, air, or an acid

"The steady dripping of water rusted the metal stopper in the sink."

adjective: of the brown color of rust