WHAT IS ETHEREAL as in quality?

Question

as in ethereal quality or nature

Answer 1

Ethereal refers to non-physical, similar to the word spiritual. An ethereal quality means there is something of which no words can properly  describe, yet one still has a sense of it.

Answer 2

Up to the XIXth century ether was the name given to a substance so subtle that light traveled through it. Different phenomena observed in light such as refraction where thus explained by the characteristics of ether. Anyway, ether was the most subtle substance so it was used in a poetical fashion to describe things that where also subtle.

Experiments on the speed of light by Michelson and Morley closed the history of this nonexistent media.