any gem variety of corundum other than the ruby, especially one of the blue varieties.
a gem of this kind.
the color of this gem, a deep blue.
resembling sapphire; deep blue: a sapphire sky.
any precious corundum gemstone that is not red, esp the highly valued transparent blue variety. A synthetic form is used in electronics and precision apparatus. Formula: Al2O3 (as modifier): a sapphire ring