adjective. Lacking material substance; insubstantial.

adjective. Lacking firmness or strength; flimsy.

adjective. Lacking basis in fact.

Not substantial; not solid: as, unsubstantial air. Not real; not having substance; imaginary; illusive: as, unsubstantial forms. Not having good substance; not strong or stout: as, an unsubstantial building; unsubstantial cloth.

Not giving substance or strength; weak; not strengthening or invigorating.

adjective. Lacking in matter or substance; visionary; chimerical.

adjective. Alternative form of insubstantial.

adjective. lacking material form or substance; unreal

""Something like a London fog" it has been called, "only a dust fog," – an animated fog in which everything unsubstantial is fair prey."

aerial  aeriform  aery  airy  ethereal  

baseless  chimerical  delusive  diaphanous  dreamlike  

Barmecidal  Barmecide  adulterated  airy  apparent