WordWeb Online

1. Surprising greatly
   "the dog was capable of astonishing tricks";
   - amazing, incredible
    
2. So surprisingly impressive as to stun or overwhelm
   "such an enormous response was astonishing";
   - astounding, staggering, stupefying

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

See also: impressive, surprising

Type of: surprise