flabbergasted
adjective /ˈflæbəɡɑːstɪd/
  /ˈflæbərɡæstɪd/
 [not usually before noun] (informal)- extremely surprised and/or shocked synonym astonished
- Friends were flabbergasted by the news that they’d split up.
 - She was too flabbergasted to speak.
 
Word Originlate 18th cent.: of unknown origin.