1. A deep blue semi-precious stone which has been prized since antiquity for its opaque to translucent blue, violet-blue, or greenish-blue colors: A lapis lazuli has been described as a deep-blue mineral composed primarily of lazurite (a mineral with sulfate, sulfur, and chloride) which is used mainly as a gem or as a pigment (coloring powder).
2. Etymology: from Latin lapis. "stone" + lazuli, the genitive form of Medieval Latin lazulum; from Arabic lazaward, from Persian lajward, "blue stone".