Ru·by n.; pl. Rubies
 1. Min. A precious stone of a carmine red color, sometimes verging to violet, or intermediate between carmine and hyacinth red.  It is a red crystallized variety of corundum.
 Note: ☞ Besides the true or Oriental ruby above defined, there are the balas ruby, or ruby spinel, a red variety of spinel, and the rock ruby, a red variety of garnet.
    Of rubies, sapphires, and pearles white.   --Chaucer.
 2. The color of a ruby; carmine red; a red tint.
    The natural ruby of your cheeks.   --Shak.
 3. That which has the color of the ruby, as red wine. Hence, a red blain or carbuncle.
 4. Print. See Agate, n., 2. [Eng.]
 5. Zool. Any species of South American humming birds of the genus Clytolaema. The males have a ruby-colored throat or breast.
 Ruby of arsenic, Ruby of sulphur Chem., a glassy substance of a red color and a variable composition, but always consisting chiefly of the disulphide of arsenic; -- called also ruby sulphur.
 Ruby of zinc Min., zinc sulphide; the mineral zinc blende or sphalerite.
 Ruby silver Min., red silver. See under Red.