greatly shock or surprise
flabbergast - shock
If something manages to ‘flabbergast’ you, then it is so unexpected that it leaves you temporarily lost for words or unsure of how to react. For that reason, this informal word is generally only used in relation to something major that is astonishing in either a good or bad way. Most commonly seen in its adjective form ‘flabbergasted’.
I thought you took the unexpected news of the factory closure remarkably well. You certainly didn’t let it flabbergast you.
Upon discovering that my assistant was leaking information about me to the press, I was utterly flabbergasted. I trusted him more than anybody.
When I set up my business I never thought that 5 years later somebody would offer me £10 million for it. I’m totally flabbergasted!