Definition of rust

The word "rust" has its roots in Old English. The original term was "rysstan" or "rystian", which was derived from the Proto-Germanic word "*rusiz" and the Proto-Indo-European root "*reus-", both of which meant "to break off" or "to crack". In Middle English (circa 11th to 15th centuries), the word "rust" evolved to refer specifically to the reddish-brown oxide coating that forms on iron and steel due to oxidation. This process, known as rusting, occurs when iron or steel is exposed to air and moisture. Today, the word "rust" can also be used more broadly to describe the decay or corrosion of materials, as well as to rhyme with other words, such as "dust" or "fust". Despite its origins in the physical process of corrosion, the word "rust" has taken on a wide range of meanings and uses over the centuries.