When something is rusty, it has become covered with rust, the reddish-brown coating that forms on iron and steel when they're exposed to moisture and air. An old bicycle left outside for years might have rusty handlebars and a rusty chain. Rust makes metal rough, flaky, and weak, and it can eventually cause metal objects to fall apart if left unchecked.

The word also describes skills or knowledge that have gotten weak or clumsy from not being used. If you haven't played piano all summer, your fingers might feel rusty when you sit down for your first lesson in the fall. A soccer player who missed practice for a month might say she's rusty when she returns to the field. Your Spanish might get rusty if you don't practice it over summer vacation.

In this second sense, rusty captures that feeling of knowing you used to be good at something but finding it harder than you remember. The good news: just as you can clean rust off metal (though it takes work), you can shake off rusty skills with practice. After a few piano sessions, your fingers remember. After a few games, that soccer player's timing comes back.