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]