(1):

(a.) 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.

(2):

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

(3):

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