1. Characterized by lightness and insubstantiality; as impalpable or intangible as air
   "The etherial music floated through the hall";
   - aeriform, aerial, airy, aery, ethereal
    
2. Characterized by unusual lightness and delicacy
   "The etherial music floated through the concert hall";
   - ethereal, gossamer
    
3. Of heaven or the spirit
   "Her etherial beauty seemed almost supernatural";
   - celestial, ethereal, supernal
    
4. (chemistry) of, containing or dissolved in ether
   "etherial solution";
   - ethereal

See also: delicate, heavenly, insubstantial, unreal, unsubstantial