vacuous in WordNet English dictionary

1. devoid of intelligence
   asinine  fatuous  inane  mindless  vacuous 
   
2. void of expression
   "a blank stare"
   blank  vacuous 
   
3. devoid of significance or point
   "empty promises"; "a hollow victory"; "vacuous comments"
   empty  hollow  vacuous 
   
4. devoid of matter
   "a vacuous space"
   vacuous