What is "ethereal oil"

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.

   Go, heavenly guest, ethereal messenger.
   --Milton.

2. Consisting of ether; hence, exceedingly light or airy; tenuous; spiritlike; characterized by extreme delicacy, as form, manner, thought, etc.

   Vast chain of being, which from God began, Natures ethereal, human, angel, man.
   --Pope.

3. (Chem.) Pertaining to, derived from, or resembling, ether; as, ethereal salts.

   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.