The Collaborative International Dictionary of English v.0.48:

Ethereal \E*the"re*al\, a.
   1. Pertaining to the hypothetical upper, purer air, or to the
      higher regions beyond the earth or beyond the atmosphere;
      celestial; as, ethereal space; ethereal regions.
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            Go, heavenly guest, ethereal messenger. --Milton.
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   2. Consisting of ether; hence, exceedingly light or airy;
      tenuous; spiritlike; characterized by extreme delicacy, as
      form, manner, thought, etc.
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            Vast chain of being, which from God began,
            Natures ethereal, human, angel, man.  --Pope.
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   3. (Chem.) Pertaining to, derived from, or resembling, ether;
      as, ethereal salts.
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   Ethereal oil. (Chem.) See Essential oil, under
      Essential.

   Ethereal oil of wine (Chem.), a heavy, yellow, oily liquid
      consisting essentially of etherin, etherol, and ethyl
      sulphate. It is the oily residuum left after
      etherification. Called also heavy oil of wine
      (distinguished from oil of wine, or [oe]nanthic ether).

   Ethereal salt (Chem.), a salt of some organic radical as a
      base; an ester.
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