of the brown color of rust
"The old fence posts were covered in a thick layer of rusty metal that stained the surrounding grass."
impaired in skill by neglect
"After years away from playing, her tennis skills were rusty when she finally stepped onto the court again."
Marked or corroded by rust.
"The old tin can had become rusty, leaving a foul, metallic taste that made me gag when I opened it."
Discolored and rancid; reasty.
In plain English: Rusty means covered with reddish-brown flaky corrosion that happens when metal is left exposed to air and moisture for too long.
"The old tools were covered in rusty red dust after sitting outside all winter."
A male given name
"Rusty is the nickname that my grandfather has used since he was a boy."
The word "rusty" comes from Middle English and Old English forms that directly mean the same thing as it does today. It entered modern usage simply by adding the suffix "-y" to describe something covered in rust.