flabbergasted vs thunderstruck

flabbergasted and thunderstruck both are adjectives.

Word	Noun	Adjective	Verb	Adverb
flabbergasted	No	Yes	No	No
thunderstruck	No	Yes	No	No

As adjectives, flabbergasted and thunderstruck are synonyms defined as:

flabbergasted and thunderstruck: as if struck dumb with astonishment and surprise

Other synonyms of flabbergasted include dumbfounded, dumbstricken, dumbstruck, dumfounded, stupefied.

flabbergasted (adjective)	thunderstruck (adjective)
as if struck dumb with astonishment and surprise	as if struck dumb with astonishment and surprise