ru·by / ˈroōbē/ • n. (pl. -bies) a precious stone consisting of corundum in color varieties varying from deep crimson or purple to pale rose. ∎  an intense purplish-red color. ∎ Printing an old type size equal to 5¹/₂ points (smaller than nonpareil and larger than pearl).

ruby a precious stone consisting of corundum in colour varieties varying from deep crimson or purple to pale rose (the term pigeon's blood is sometimes used of ruby of a particularly deep shade).

The name may also be used for the less valuable spinel ruby, a deep red variety of the mineral spinel. The ruby may also be taken as the type of something exceedingly precious, as in the biblical passage.
ruby wedding the fortieth (or occasionally, the forty-fifth) anniversary of a wedding; the name is recorded from the early 20th century.

ruby Gem variety of the mineral corundum (aluminium oxide), whose characteristic red colour is due to impurities of chromium and iron oxides. The traditional source of rubies is Burma. Today, synthetic rubies are widely used in industry.

ruby See CORUNDUM; and SPINEL.

ruby XIV. — OF. rubi (mod. rubis) — medL. rubīnus, sb. use of adj. f. base of L. rubeus, ruber RED.