The Collaborative International Dictionary of English v.0.48:

Astound \As*tound"\, v. t. [imp. & p. p. Astounded, [Obs.]
   Astound; p. pr. & vb. n. Astounding.] [See Astound, a.]
   1. To stun; to stupefy.
      [1913 Webster]

            No puissant stroke his senses once astound.
                                                  --Fairfax.
      [1913 Webster]

   2. To astonish; to strike with amazement; to confound with
      wonder, surprise, or fear.
      [1913 Webster]

            These thoughts may startle well, but not astound
            The virtuous mind.                    --Milton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

astounded \astounded\ adj.
   1. struck with an intense and usually sudden surprise
      sufficient to produce wonder or perplexity

   Syn: amazed, astonied, astonished, dumbfounded,
        flabbergasted, stunned, stupefied, thunderstruck
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

astounded
    adj 1: filled with the emotional impact of overwhelming surprise
           or shock; "an amazed audience gave the magician a
           standing ovation"; "I stood enthralled, astonished by the
           vastness and majesty of the cathedral"; "astounded
           viewers wept at the pictures from the Oklahoma City
           bombing"; "stood in stunned silence"; "stunned scientists
           found not one but at least three viruses" [syn: amazed,
           astonied, astonished, astounded, stunned]