Having the form or nature of air, or of an elastic invisible fluid; gaseous. The gases are aëriform fluids.

Figuratively, unsubstantial; unreal.

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

adjective. Pertaining to air, or having a form similar to that of air.

adjective. Light, unsubstantial, or unstable.

adjective. characterized by lightness and insubstantiality; as impalpable or intangible as air

adjective. resembling air or having the form of air

"Humboldt extends this view to the case of earthquakes unaccompanied by eruptions; but I can hardly conceive it possible that the small quantity of aeriform fluids which then escape from the fissured ground can produce such remarkable effects."

gaseous  insubstantial  unreal  unsubstantial  

crystalloid  excrementitious  extravascular  glairy  hydrothermal  

gaseous