1. An unit of length used in astronomy defined as 149597870700m, roughly equal to the mean distance between the Earth and the Sun (approximately 93 million miles or 150 million kilometres)
   "The comet's orbit extended beyond two AUs";
   - astronomical unit

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
   "Prospectors discovered Au in the river bed";
   - gold, atomic number 79

Derived forms: Aus, AUs

Type of: astronomy unit, noble metal

Part of: dental gold, gold, gold foil, gold leaf, graphic tellurium, sylvanite

Encyclopedia: AU