The Collaborative International Dictionary of English v.0.48:

Astonish \As*ton"ish\, v. t. [imp. & p. p. Astonished; p. pr.
   & vb. n. Astonishing.] [OE. astonien, astunian, astonen,
   OF. estoner, F. ['e]tonner, fr. L. ex out + tonare to
   thunder, but perhaps influenced by E. stun. See Thunder,
   Astound, Astony.]
   1. To stun; to render senseless, as by a blow. [Obs.]
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            Enough, captain; you have astonished him. [Fluellen
            had struck Pistol].                   --Shak.
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            The very cramp-fish [i. e., torpedo] . . . being
            herself not benumbed, is able to astonish others.
                                                  --Holland.
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   2. To strike with sudden fear, terror, or wonder; to amaze;
      to surprise greatly, as with something unaccountable; to
      confound with some sudden emotion or passion.
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            Musidorus . . . had his wits astonished with sorrow.
                                                  --Sidney.
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            I, Daniel . . . was astonished at the vision. --Dan.
                                                  viii. 27.
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   Syn: To amaze; astound; overwhelm; surprise.

   Usage: Astonished, Surprised. We are surprised at what is
          unexpected. We are astonished at what is above or
          beyond our comprehension. We are taken by surprise. We
          are struck with astonishment. --C. J. Smith. See
          Amaze.
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WordNet (r) 3.0 (2006):

astonish
    v 1: affect with wonder; "Your ability to speak six languages
         amazes me!" [syn: amaze, astonish, astound]