The word brass has two main meanings:

1. A shiny, golden-colored metal made by mixing copper and zinc. Brass is harder than copper alone, which makes it perfect for objects that need to be both strong and workable. Doorknobs, musical instruments, and decorative fixtures are often made from brass because it resists rust, looks attractive, and can be shaped and polished beautifully. Ancient civilizations discovered that mixing these two metals created something more useful than either metal by itself.
2. The section of an orchestra or band that includes trumpets, trombones, French horns, and tubas. These instruments are called brass instruments because they're traditionally made from brass, and players make sounds by buzzing their lips into a mouthpiece. When a conductor tells the brass section to play louder, those powerful, bright sounds can fill an entire concert hall. The brass section often plays fanfares and bold melodies that demand attention.

People sometimes use brass to describe bold confidence, as when someone has “the brass” to do something daring. Military officers' insignia are called brass, too, which led to calling high-ranking officers “the brass.”