insubstantial
in-sub-stan-tial
adjective
Lacking strength, solidity, or importance; not firm, real, or significant.
"The old wooden bridge felt insubstantial underfoot."
Thesaurus
Synonyms: unwholesome, flimsy, weak, aery, airy, stringy, hollow, wraithlike, unreal, aeriform, unsubstantial, aerial
Antonyms: material, real, substantial