Definition of: ether

(ē′thər) noun
1. Chem. a A colorless, mobile, volatile, aromatic liquid compound, ethyl oxide, (C₂H₅)₂O, made by the action of sulfuric acid on alcohol: used as an anesthetic and solvent. b Any of a group of organic compounds in which an oxygen atom is joined with two organic radicals.
2. A solid or semisolid, perfectly elastic medium formerly assumed to pervade all of space and to be responsible for the transmission of light, heat, gravitational effects, and all forms of energy and radiation.
3. The upper air. Also spelled aether (for defs. 2 and 3). [<L aether sky <Gk. aithēr <aithein burn, shine]