unsubstantial
un-sub-stan-tial
adjective
Lacking firmness, solidity, or real importance; not strong, significant, or well-founded.
"The evidence presented was unsubstantial."
Thesaurus
Synonyms: aery, airy, stringy, hollow, wraithlike, unreal, aeriform, aerial, ethereal, shadowy, insubstantial
Antonyms: material, real, substantial