A clear hard variety of corundum used as a gemstone that is usually blue but may be any color except red, A precious stone next in hardness to the diamond, and nearly as valuable when of fine quality_ a variety of the mineral corundum, a type of South American hummingbird, adjective_ of a deep blue colour, of something having the color of a blue sapphire, Of or resembling sapphire; sapphirine; blue