The Collaborative International Dictionary of English v.0.48:

Frustrate \Frus"trate\, a. [L. frustratus, p. p. of frustrare,
   frustrari, to deceive, frustrate, fr. frustra in vain, witout
   effect, in erorr, prob. for frudtra and akin to fraus, E.
   fraud.]
   Vain; ineffectual; useless; unprofitable; null; voil;
   nugatory; of no effect. "Our frustrate search." --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Frustrate \Frus"trate\, v. t. [imp. & p. p. Frustrated; p. pr.
   & vb. n. Frustrating.]
   1. To bring to nothing; to prevent from attaining a purpose;
      to disappoint; to defeat; to baffle; as, to frustrate a
      plan, design, or attempt; to frustrate the will or
      purpose.
      [1913 Webster]

            Shall the adversary thus obtain
            His end and frustrate thine ?         --Milton.
      [1913 Webster]

   2. To make null; to nullifly; to render invalid or of no
      effect; as, to frustrate a conveyance or deed.

   Syn: To balk; thwart; foil; baffle; defeat.
        [1913 Webster]

WordNet (r) 3.0 (2006):

frustrate
    v 1: hinder or prevent (the efforts, plans, or desires) of;
         "What ultimately frustrated every challenger was Ruth's
         amazing September surge"; "foil your opponent" [syn:
         thwart, queer, spoil, scotch, foil, cross,
         frustrate, baffle, bilk]
    2: treat cruelly; "The children tormented the stuttering
       teacher" [syn: torment, rag, bedevil, crucify, dun,
       frustrate]

Moby Thesaurus II by Grady Ward, 1.0:

117 Moby Thesaurus words for "frustrate":
   annul, anticipate, arrest, baffle, balk, bar, beat, bilk, blast,
   block, brave, bring to nothing, buffalo, buffer, cancel,
   cancel out, cast down, challenge, check, checkmate, circumvent,
   come to nothing, confound, confront, conquer, contravene, counter,
   counteract, counterbalance, countermand, counterwork, cripple,
   cross, dash, deceive, defeat, defeat expectation, defy, destroy,
   disappoint, discomfit, disconcert, discountenance, discourage,
   dish, disillusion, disrupt, dissatisfy, elude, evade, exasperate,
   flummox, foil, forbid, forestall, get around, get round,
   give the runaround, give the slip, go one better, halt, hamper,
   hamstring, hinder, impede, inhibit, interrupt, invalidate,
   knock the chocks, let down, lick, negate, negativate, negative,
   neutralize, nonplus, nullify, obstruct, obviate, offset, outfigure,
   outflank, outgeneral, outguess, outmaneuver, outplay, outreach,
   outsmart, outwit, overcome, overreach, pass the buck, perplex,
   preclude, prevent, prohibit, redress, repel, repulse, ruin,
   sabotage, scotch, spike, spoil, stonewall, stop, stultify, stump,
   stymie, tantalize, tease, thwart, undo, upset, victimize, vitiate,
   void