(Roman mythology) The god-personification of the bright, glowing upper air of heaven. He is the Roman counterpart of Aether.

(Mormonism) The ancient American prophet of Mormon theology who wrote the Book of Ether in the Book of Mormon.

(cryptocurrencies) A unit of the Ethereum digital currency, ETH.

(uncountable, literary or poetic) A substance believed to fill the upper regions of the atmosphere, also referred to as the air, sky, heavens, or nothingness.

(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, colloquial) The atmosphere or space as a medium for broadcasting radio and television signals; also, a notional space through which Internet and other digital communications take place; cyberspace.

(uncountable, colloquial) A particular quality created by or surrounding an object, person, or place; an atmosphere, an aura.

(uncountable, organic chemistry) Diethyl ether (C4H10O), an organic compound with a sweet odour used in the past as an anaesthetic.

(countable, organic chemistry) Any of a class of organic compounds containing an oxygen atom bonded to two hydrocarbon groups.

(uncountable) Starting fluid.

(cryptocurrencies) Alternative letter-case form of Ether

(transitive, slang) To viciously humiliate or insult.