1) Aerial 2) Aeriform 3) Aery 4) Airy 5) Elusive 6) Ethereal 7) Flimsy 8) Immaterial 9) Indefinable 10) Indescribable 11) Lacking in nutritive value 12) Nonmaterial 13) Not solid or firm 14) Not substantial or real 15) Paper 16) Shadowy 17) Subtle 18) Unreal 19) Unsubstantial 20) Vague 21) Weak 22) Wraithlike 1) Aery 2) Airy 3) Ethereal 4) Flimsy 5) Fragile 6) Frothy 7) Imaginary 8) Incorporeal 9) Inessential 10) Jejune 11) Light 12) Meagre 13) Nonmaterial 14) Paper 15) Porous 16) Tenuous 17) Unsubstantial 18) Unwholesome 19) Weightless 20) Wispish 21) Wraithlike 
• (a.) Unsubstantial; not real or strong.
In`sub·stan'tial adjective Unsubstantial; not real or strong. ' Insubstantial pageant.' [ R.] Shak. 
[adj] - lacking in nutritive value 2. [adj] - lacking material form or substance
jejune adjective lacking in nutritive value; `the jejune diets of the very poor`
not substantial or real; lacking substance: an insubstantial world of dreams. · not solid or firm; weak; flimsy. · not substantial in amount or size; inconsiderable: an insubstantial sum.