The Collaborative International Dictionary of English v.0.48:

Confound \Con*found"\ (k[o^]n*found"), v. t. [imp. & p. p.
   Confounded; p. pr. & vb. n. Confounding.] [F. confondre,
   fr. L. confundere, -fusum, to pour together; con- + fundere
   to pour. See Fuse to melt, and cf. Confuse.]
   1. To mingle and blend, so that different elements can not be
      distinguished; to confuse.
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            They who strip not ideas from the marks men use for
            them, but confound them with words, must have
            endless dispute.                      --Locke.
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            Let us go down, and there confound their language.
                                                  --Gen. xi. 7.
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   2. To mistake for another; to identify falsely.
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            They [the tinkers] were generally vagrants and
            pilferers, and were often confounded with the
            gypsies.                              --Macaulay.
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   3. To throw into confusion or disorder; to perplex; to strike
      with amazement; to dismay.
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            The gods confound...
            The Athenians both within and out that wall. --Shak.
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            They trusted in thee and were not confounded. --Ps.
                                                  xxii. 5.
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            So spake the Son of God, and Satan stood
            A while as mute, confounded what to say. --Milton.
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   4. To destroy; to ruin; to waste. [Obs.]
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            One man's lust these many lives confounds. --Shak.
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            How couldst thou in a mile confound an hour? --Shak.

   Syn: To abash; confuse; baffle; dismay; astonish; defeat;
        terrify; mix; blend; intermingle. See Abash.
        [1913 Webster]

WordNet (r) 3.0 (2006):

confound
    v 1: be confusing or perplexing to; cause to be unable to think
         clearly; "These questions confuse even the experts"; "This
         question completely threw me"; "This question befuddled
         even the teacher" [syn: confuse, throw, fox,
         befuddle, fuddle, bedevil, confound,
         discombobulate]
    2: mistake one thing for another; "you are confusing me with the
       other candidate"; "I mistook her for the secretary" [syn:
       confuse, confound]