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.
      [1913 Webster]

            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.
      [1913 Webster]

            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.]
      [1913 Webster]

            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]

Moby Thesaurus II by Grady Ward, 1.0:

251 Moby Thesaurus words for "confound":
   abash, accurse, addle, adulterate, alloy, amaze, anathematize,
   answer, answer conclusively, appall, argue down, astonish, astound,
   awe, awestrike, baffle, balk, ball up, bamboozle, beat, bedaze,
   bedazzle, befog, bewilder, blaspheme, blast, blur,
   blur distinctions, boggle, bollix up, bowl down, bowl over, brave,
   break, bring to ruin, buffalo, canker, cap, cast down, chagrin,
   challenge, cheapen, checkmate, circumvent, coarsen, complicate,
   condemn, confound, confront, confuse, confute, consume,
   contaminate, contradict, contravene, controvert, corrupt, counter,
   counteract, countermand, counterwork, cross, crush, curse, damn,
   darn, dash, daze, dazzle, deal destruction, debase, debauch,
   decimate, defeat, defile, deflower, defy, degenerate, degrade,
   demolish, denature, deny, deprave, depredate, desecrate, desolate,
   despoil, destroy, devalue, devastate, devour, discomfit,
   discompose, disconcert, disconfirm, discountenance, dish, dismay,
   dismiss, dispose of, disrupt, dissolve, distort, dumbfound,
   dumbfounder, elude, embarrass, embrangle, engorge, entangle, evert,
   excommunicate, execrate, faze, finish, flabbergast, floor, flummox,
   foil, foul up, frustrate, fuddle, fulminate against, fumble,
   garble, get, gobble, gobble up, gut, gut with fire, havoc, hex,
   implicate, imprecate, incinerate, infect, involve, jumble,
   jumble together, keep in suspense, knock the chocks, knot,
   lay in ruins, lay waste, lick, louse up, maze, mess up, misdeem,
   misidentify, misuse, mix, mix up, mortify, muck up, muddle,
   mystify, nonplus, overlook distinctions, overthrow, overturn,
   overwhelm, panic, paralyze, parry, perplex, pervert, petrify, pi,
   play hob with, poison, pollute, pose, prostitute, put out,
   put to flight, put to rout, put to silence, puzzle, ramify, rattle,
   ravage, ravel, ravish, rebut, reduce to silence, refute, riffle,
   rout, ruin, ruinate, sabotage, scatter, scotch, scramble, screw up,
   settle, shipwreck, shuffle, shut up, silence, smash all opposition,
   snafu, snarl, snarl up, spike, spoil, squash, squelch, stagger,
   stampede, startle, stick, stonewall, strike dead, strike dumb,
   strike with wonder, stumble, stump, stun, stupefy, subvert,
   surprise, swallow up, taint, take aback, tangle, throw,
   throw a whammy, throw into confusion, throw into disorder,
   thunder against, thwart, tumble, twist, ulcerate, undermine,
   unleash destruction, unleash the hurricane, upheave, upset,
   vandalize, vaporize, violate, vitiate, vulgarize, warp, waste,
   wrack, wreak havoc, wreck