WordWeb Online

1. Characterized by lightness and insubstantiality; as impalpable or intangible as air
   - aeriform, aerial, airy, aery, ethereal
    
2. Characterized by unusual lightness and delicacy
   - ethereal, gossamer
    
3. (chemistry) of, containing or dissolved in ether
   - ethereal
    
4. Of heaven or the spirit
   "etherial peace";
   - celestial, ethereal, supernal

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