DUMBFOUNDED

dumbfounded, dumfounded, flabbergasted, stupefied, thunderstruck, dumbstruck, dumbstricken

(adjective) as if struck dumb with astonishment and surprise; “a circle of policemen stood dumbfounded by her denial of having seen the accident”; “the flabbergasted aldermen were speechless”; “was thunderstruck by the news of his promotion”

Source: WordNet® 3.1

Adjective

dumbfounded (comparative more dumbfounded, superlative most dumbfounded)

shocked and speechless.

Synonyms

• amazed, astonished, astounded, confounded, flabbergasted, perplexed, shocked, speechless, stunned, stupefied, surprised

Verb

dumbfounded

simple past tense and past participle of dumbfound

Source: Wiktionary