Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
dumbstricken is an adjective meaning "as if struck dumb with astonishment and surprise". It carries one recorded sense.
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”
Definitions, synonyms and semantic relations for dumbstricken come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.