AERIFORM
aeriform, aerial, airy, aery, ethereal
(adjective) characterized by lightness and insubstantiality; as impalpable or intangible as air; “figures light and aeriform come unlooked for and melt away”- Thomas Carlyle; “aerial fancies”; “an airy apparition”; “physical rather than ethereal forms”
aeriform, airlike
(adjective) resembling air or having the form of air
Source: WordNet® 3.1
Etymology
Adjective
aeriform
Pertaining to air.
Having a form similar to that of air.
Light, unsubstantial, or unstable.
Source: Wiktionary
A"ër*i*form, a. Etym: [L. aër air + -form: cf. F. aériforme.]
Definition: Having the form or nature of air, or of an elastic fluid;
gaseous. Hence fig.: Unreal.
Source: Webster’s Unabridged Dictionary 1913 Edition