in·sub·stan·tial 
(ĭn′səb-stănshəl)
(ĭn′səb-stănshəl)adj.
1. Not firm or solid; weak or flimsy: a shed made of insubstantial materials.
2. Very small or negligible, as in importance, size, or amount: an insubstantial volume of traffic.
3. Lacking or appearing to lack substance or reality: "the insubstantial vapor of an autumn field" (Loren Eiseley).
in′sub·stan′ti·ali·ty (-shē-ălĭ-tē) n.