au meaning and definition

AU noun

Definition of Au (noun)

1. 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
   • synonyms: atomic number 79, gold
2. 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)
   • synonyms: Astronomical Unit