1.  ethereal(s = adj.all) aerial, aeriform, aery, airy - characterized by lightness and insubstantiality; as impalpable or intangible as air; "figures light and aeriform come unlooked for and melt away"; "aerial fancies"; "an airy apparition"; "physical rather than ethereal forms"

2.  ethereal(a = adj.pert) Array - of or containing or dissolved in ether; "ethereal solution"
Derived forms noun ether₄, noun ether₂

3.  ethereal(s = adj.all) celestial, supernal - of heaven or the spirit; "celestial peace"; "ethereal melodies"; "the supernal happiness of a quiet death"
Derived form noun ether₁

4.  ethereal(s = adj.all) gossamer - characterized by unusual lightness and delicacy; "this smallest and most ethereal of birds"; "gossamer shading through his playing"

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. [1913 Webster]
"Go, heavenly guest, ethereal messenger." [1913 Webster]

2.  Consisting of ether; hence, exceedingly light or airy; tenuous; spiritlike; characterized by extreme delicacy, as form, manner, thought, etc. [1913 Webster]
"Vast chain of being, which from God began,
Natures ethereal, human, angel, man." [1913 Webster]

3.  Pertaining to, derived from, or resembling, ether; as, ethereal salts. [1913 Webster]

ethereal, adj. (also etherial)
1 light, airy.
2 highly delicate, esp. in appearance.
3 heavenly, celestial.
4 Chem. of or relating to ether.

Derivative:
ethereality n. ethereally adv.

Etymology:
L aethereus, -ius f. Gk aitherios (as ETHER)

N  unsubstantiality, insubstantiality, nothingness, nihility, no degree, no part, no quantity, no thing, nothing, naught, nil, nullity, zero, cipher, no one, nobody, never a one, ne'er a one, no such thing, none in the world, nothing whatever, nothing at all, nothing on earth, not a particle, all talk, moonshine, stuff and nonsense, matter of no importance, matter of no consequence, thing of naught, man of straw, John Doe and Richard Roe, faggot voter, nominis umbra, nonentity, flash in the pan, vox et praeterea nihil, shadow, phantom, dream, ignis fatuus, such stuff as dreams are made of, air, thin air, vapor, bubble, baseless fabric of a vision, mockery, hollowness, blank, void, inanity, fool's paradise, unsubstantial, baseless, groundless, ungrounded, without foundation, having no foundation, visionary, immaterial, spectral, dreamy, shadowy, ethereal, airy, cloud built, cloud formed, gossamery, illusory, insubstantial, unreal, vacant, vacuous, empty, eviscerated, blank, hollow, nominal, null, inane, there's nothing in it, an ocean of dreams without a sound.

N  levity, lightness, imponderability, buoyancy, volatility, feather, dust, mote, down, thistle, down, flue, cobweb, gossamer, straw, cork, bubble, balloon, float, buoy, ether, air, leaven, ferment, barm, yeast, lighter-than-air balloon, helium balloon, hydrogen balloon, hot air balloon, convection, thermal draft, thermal, light, subtile, airy, imponderous, imponderable, astatic, weightless, ethereal, sublimated, gossamery, suberose, suberous, uncompressed, volatile, buoyant, floating, portable, light as a feather, light as a thistle, light as air, lighter than air, rise like a balloon, float like a balloon.

N  gaseity, vaporousness, flatulence, flatulency, volatility, aeration, aerification, elastic fluid, gas, air, vapor, ether, steam, essence, fume, reek, effluvium, flatus, cloud, ammonia, ammoniacal gas, volatile alkali, vacuum, partial vacuum, pneumatics, pneumatostatics, aerostatics, aerodynamics, gasmeter, gasometer, air bladder, swimming bladder, sound, (of a fish), gaseous, aeriform, ethereal, aerial, airy, vaporous, volatile, evaporable, flatulent.