The Collaborative International Dictionary of English v.0.48:

Aston \As*ton"\, Astone \As*tone"\, v. t. [imp. & p. p.
   Astoned, Astond, or Astound.] [See Astonish.]
   To stun; to astonish; to stupefy. [Obs.] --Chaucer.
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The Collaborative International Dictionary of English v.0.48:

Astound \As*tound"\, a. [OE. astouned, astound, astoned, p. p.
   of astone. See Astone.]
   Stunned; astounded; astonished. [Archaic] --Spenser.
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         Thus Ellen, dizzy and astound.
         As sudden ruin yawned around.            --Sir W.
                                                  Scott.
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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.
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            No puissant stroke his senses once astound.
                                                  --Fairfax.
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   2. To astonish; to strike with amazement; to confound with
      wonder, surprise, or fear.
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            These thoughts may startle well, but not astound
            The virtuous mind.                    --Milton.
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WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "astound":
   abash, amaze, appall, astonish, awe, awestrike, bedaze, bedazzle,
   bewilder, boggle, bowl down, bowl over, confound, daze, dazzle,
   discomfit, disconcert, dismay, dumbfound, dumbfounder, flabbergast,
   floor, overwhelm, paralyze, perplex, petrify, put out, shock,
   stagger, startle, strike dead, strike dumb, strike with wonder,
   stun, stupefy, surprise, take aback