Having the form or nature of air, or of an elastic fluid; gaseous. Hence fig.: Unreal.

resembling air or having the form of air

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"