ether
n//ˈi.θɚ//eter
(uncountable, literary, or, poetic) The substance formerly supposed to fill the upper regions of the atmosphere above the clouds, in particular as a medium breathed by deities.
(uncountable, physics, historical) Often as aether and more fully as luminiferous aether: a substance once thought to fill all unoccupied space that allowed electromagnetic waves to pass through it and interact with matter, without exerting any resistance to matter or energy; its existence was disproved by the 1887 Michelson–Morley experiment and the theory of relativity propounded by Albert Einstein (1879–1955).
(uncountable, organic compound) Diethyl ether (C4H10O), an organic compound with a sweet odour used in the past as an anaesthetic.
(countable, organic compound) Any of a class of organic compounds containing an oxygen atom bonded to two hydrocarbon groups.