Meaning

noun a transparent piece of ruby that has been cut and polished and is valued as a precious gem

noun a transparent deep red variety of corundum; used as a gemstone and in lasers

noun a deep and vivid red color

originFrom Middle English ruby, rube, from Old French rubi, from Medieval Latin rubīnus. Doublet of rubi and rubine. Sense 7 (“pronunciation guide”) is from the British 5½-point type size (sense 6), used for annotations in printed documents.

Etymology from Wiktionary, CC BY-SA 3.0