What does flabbergasted mean?

Answer 1

Flabbergasted means "astounded, thunderstruck, astonished, struck dumb."

In other words, it means to be overcame with surprise and bewilderment, to be overwhelmed with shock or wonder, to be astonished, to be stroked with wonder (especially by extraordinary statements), or to shock someone (usually by telling them something they were not expecting).

Used in an example sentence: "He was flabbergasted when we told him how cheap it was."

Surprised, astonished and flabbergasted all mean shocked and amazed.

Answer 2

To be flabbergasted, is to be surprised or shocked, often leading to speechlessness.

As in:

John was flabbergasted when he discovered his wife is doing sex in bed with the postman.