UK:*UK and possibly other pronunciationsUK and possibly other pronunciations/ˈflæbəˌɡɑːst/US:USA pronunciation: IPA and respellingUSA pronuncation: IPA/ˈflæbɚˌgæst/ ,USA pronunciation: respelling(flabər gast′)

WordReference Random House Learner's Dictionary of American English © 2020
flab•ber•gast /ˈflæbɚˌgæst/USA pronunciation   v. [+ object]
  1. to overcome with surprise and bewilderment;
    astound:The news of his promotion flabbergasted me.

WordReference Random House Unabridged Dictionary of American English © 2020
flab•ber•gast  (flabər gast′),USA pronunciation v.t. 
  1. to overcome with surprise and bewilderment;
flabber•gast′er, n. 
  • variant of flabagast (perh. flabb(y) + aghast) 1765–75
    amaze, astonish, stagger, nonplus, confound;
    perplex, confuse, mystify.

Collins Concise English Dictionary © HarperCollins Publishers::
flabbergast /ˈflæbəˌɡɑːst/ vb (transitive)
  1. informal to overcome with astonishment; amaze utterly; astound
Etymology: 18th Century: of uncertain origin
'flabbergast' also found in these entries (note: many are not synonyms or translations):
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