Definition of "Ether" :

noun: a colorless volatile highly flammable liquid formerly used as an inhalation anesthetic

noun: a medium that was once supposed to fill all space and to support the propagation of electromagnetic waves

noun: any of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom

noun: the fifth and highest element after air and earth and fire and water; was believed to be the substance composing all heavenly bodies