- 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: Al 2 O 3
- (as modifier)
- the blue colour of sapphire
- (as adjective)
