Insubstantial rhymes with:
substantial, substantial, substantial, circumstantial, substantial, circumstantial, substantial, circumstantial, substantial, circumstantial, consequential, credential, deferential, existential, exponential, hentschel, inconsequential, influential, konczal, nonessential, preferential, presidential, providential, prudential, residential, reverential, sequential, substantial, tangential, torrential, vice-presidential, winchell