flabbergasted

US: /ˈfɫæbɝˌɡæstɪd/
UK: /flˈæbəɡˌɑːstɪd/

Advanced English dictionary

+ adjective
[not usually before noun] (informal) extremely surprised and/or shocked: Friends were flabbergasted by the news that they'd split up. + She was too flabbergasted to speak.

Concise English dictionary

flabbergasts|flabbergasted|flabbergasting'flæbə(r)gæst /-gɑːst
verb
+overcome with amazement