Source : Webster's Revised Unabridged Dictionary (1913)

Insubstantial \In`sub*stan"tial\, a.
   Unsubstantial; not real or strong. ``Insubstantial pageant.''
   [R.] --Shak.

Source : WordNet®

insubstantial
     adj 1: lacking material form or substance; unreal; "as
            insubstantial as a dream"; "an insubstantial mirage on
            the horizon" [syn: {unsubstantial}, {unreal}] [ant: {substantial}]
     2: lacking in nutritive value; "the jejune diets of the very
        poor" [syn: {jejune}]