Source : Webster's Revised Unabridged Dictionary (1913)

Defeat \De*feat"\, n. [Cf. F. d['e]faite, fr. d['e]faire. See
   {Defeat}, v.]
   1. An undoing or annulling; destruction. [Obs.]

            Upon whose property and most dear life A damned
            defeat was made.                      --Shak.

   2. Frustration by rendering null and void, or by prevention
      of success; as, the defeat of a plan or design.

   3. An overthrow, as of an army in battle; loss of a battle;
      repulse suffered; discomfiture; -- opposed to victory.

Defeat \De*feat"\, v. t. [imp. & p. p. {Defeated}; p. pr. & vb.
   n. {Defeating}.] [From F. d['e]fait, OF. desfait, p. p. ofe
   d['e]faire, OF. desfaire, to undo; L. dis- + facere to do.
   See {Feat}, {Fact}, and cf. {Disfashion}.]
   1. To undo; to disfigure; to destroy. [Obs.]

            His unkindness may defeat my life.    --Shak.

   2. To render null and void, as a title; to frustrate, as
      hope; to deprive, as of an estate.

            He finds himself naturally to dread a superior Being
            that can defeat all his designs, and disappoint all
            his hopes.                            --Tillotson.

            The escheators . . . defeated the right heir of his
            succession.                           --Hallam.

            In one instance he defeated his own purpose. --A. W.
                                                  Ward.

   3. To overcome or vanquish, as an army; to check, disperse,
      or ruin by victory; to overthrow.

   4. To resist with success; as, to defeat an assault.

            Sharp reasons to defeat the law.      --Shak.

   Syn: To baffle; disappoint; frustrate.

Source : WordNet®

defeat
     n 1: an unsuccessful ending [syn: {licking}] [ant: {victory}]
     2: the feeling that accompanies an experience of being thwarted
        in attaining your goals [syn: {frustration}]
     v 1: win a victory over; "You must overcome all difficulties";
          "defeat your enemies"; "He overcame his shyness"; "She
          conquered here fear of mice"; "He overcame his
          infirmity"; "Her anger got the better of her and she
          blew up" [syn: {get the better of}, {overcome}]
     2: thwart the passage of; "kill a motion"; "he shot down the
        student's proposal" [syn: {kill}, {shoot down}, {vote down},
         {vote out}]