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.

adjective

real , strong , substantial

adjective

aerial , airy , chimerical , decrepit , ephemeral , false , fanciful , feeble , flimsy , fly-by-night * , fragile , frail , idle , illusory , immaterial , imponderable , incorporeal , infirm , intangible , metaphysical , petty , poor , puny , slender , slight , tenuous , thin , too little too late , unreal , unsound , unsubstantial , bodiless , discarnate , disembodied , nonphysical , spiritual , unbodied , uncorporal , delicate , weak , weakly , fine , imaginary , small