Adjective: unsubstantial ,ún-sub'stan-shul
- Lacking solid basis, importance, or significance
"his unsubstantial arguments failed to convince anyone";
- insubstantial
- Lacking material form or substance; unreal
"as unsubstantial as a dream";
- insubstantial, unreal
See also: aerial, aeriform, aery, airy, ethereal, etherial, hollow, immaterial, nonmaterial, shadowy, solidness, stringy, substantiality, substantialness, wraithlike