Synonyms for Astounding (same or very similar meaning)
WordNet sense 1 (so surprisingly impressive as to stun or overwhelm):
astonishing, staggering, stupefying
WordNet sense 2 (making a strong or vivid impression):
impressive
WordNet sense 3 (bewildering or striking dumb with wonder):
dumbfounding, dumfounding
WordNet sense 4 (beyond belief or understanding):
unbelievable
From the ODE community, based on WordNet
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