dumbfounded

(verb) be a mystery or bewildering to. Synonyms: perplex, vex, stick, get, puzzle, mystify, baffle, beat, pose, bewilder, flummox, stupefy, nonplus, gravel, amaze, dumbfound. Examples: "This beats me!." "Got me--i don't know the answer!." "A vexing problem." "This question really stuck me."

(adj) as if struck dumb with astonishment and surprise. Synonyms: dumfounded, flabbergasted, stupefied, thunderstruck, dumbstruck, dumbstricken. Examples: "A circle of policement stood dumbfounded by her denial of having seen the accident." "The flabbergasted aldermen were speechless." "Was thunderstruck by the news of his promotion."