dumfounded

Adjective

• as if struck dumb with astonishment and surprise
  • a circle of policement stood dumbfounded by her denial of having seen the accident
    
  • the flabbergasted aldermen were speechless
    
  • was thunderstruck by the news of his promotion
    

Related words

• Synonyms: 
  dumbfounded , flabbergasted , stupefied , thunderstruck , dumbstruck , dumbstricken