1. (

• gold ,
• Au ,
• atomic_number_ ,

) a soft yellow malleable ductile (trivalent and univalent) metallic element; occurs mainly as nuggets in rocks and alluvial deposits; does not react with most chemicals but is attacked by chlorine and aqua regia ;

2. (

• Astronomical_Unit ,
• AU

) a unit of length used for distances within the solar system; equal to the mean distance between the Earth and the Sun (approximately 93 million miles or 150 million kilometers) ;