Synonyms for Stupefying (same or very similar meaning)
WordNet sense 1 (causing loss of physical or intellectual bearings):
disorienting
WordNet sense 2 (so surprisingly impressive as to stun or overwhelm):
astonishing, astounding, staggering
WordNet sense 3 (making a strong or vivid impression):
impressive
WordNet sense 4 (causing alarm or fear):
alarming
From the ODE community, based on WordNet
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