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1. Bewildering or striking dumb with wonder
   "These sciences revealed not only the astounding largeness of the universe but also the dumbfounding smallness of human beings";
   - dumbfounding, dumfounding
    
2. So surprisingly impressive as to stun or overwhelm
   "an astounding achievement";
   - astonishing, staggering, stupefying

1. Fill with wonder or astonishment; greatly surprise
   "Your ability to speak six languages astounds me!";
   - amaze, astonish

See also: impressive, incredible, unbelievable

Type of: surprise

Encyclopedia: Astounding