Source : Webster's Revised Unabridged Dictionary (1913)

Vacuous \Vac"u*ous\, a. [L. vacuus. See {Vacant}.]
   Empty; unfilled; void; vacant.

         Boundless the deep, because I am who fill Infinitude;
         nor vacuous the space.                   --Milton.

         That the few may lead selfish and vacuous days. --J.
                                                  Morley.

Source : WordNet®

vacuous
     adj 1: complacently or inanely foolish [syn: {asinine}, {fatuous},
            {inane}, {mindless}]
     2: devoid of significance or point; "empty promises"; "a hollow
        victory"; "vacuous comments" [syn: {empty}, {hollow}]