An Australian plant of the genus Xanthorrhoea, having a
   thick trunk crowned with a dense tuft of pendulous, grasslike leaves,
   from the center of which arises a long stem, bearing at its summit a
   dense flower spike looking somewhat like a large cat-tail. These plants
   are often called "blackboys" from the large trunks denuded and
   blackened by fire. They yield two kinds of fragrant resin, called
   Botany-bay gum, and Gum Acaroides.