Source : Webster's Revised Unabridged Dictionary (1913)

Defense \De*fense"\, Defence \De*fence"\, n. [F. d['e]fense, OF.
   defense, fem., defens, masc., fr. L. defensa (cf. LL.
   defensum), from defendere. See {Defend}, and cf. {Fence}.]
   1. The act of defending, or the state of being defended;
      protection, as from violence or danger.

            In cases of defense 't is best to weigh The enemy
            more mighty than he seems.            --Shak.

   2. That which defends or protects; anything employed to
      oppose attack, ward off violence or danger, or maintain
      security; a guard; a protection.

            War would arise in defense of the right. --Tennyson.

            God, the widow's champion and defense. --Shak.

   3. Protecting plea; vindication; justification.

            Men, brethren, and fathers, hear ye my defense.
                                                  --Acts xxii.
                                                  1.

   4. (Law) The defendant's answer or plea; an opposing or
      denial of the truth or validity of the plaintiff's or
      prosecutor's case; the method of proceeding adopted by the
      defendant to protect himself against the plaintiff's
      action.

   5. Act or skill in making defense; defensive plan or policy;
      practice in self defense, as in fencing, boxing, etc.

            A man of great defense.               --Spenser.

            By how much defense is better than no skill. --Shak.

   6. Prohibition; a prohibitory ordinance. [Obs.]

            Severe defenses . . . against wearing any linen
            under a certain breadth.              --Sir W.
                                                  Temple.

Defense \De*fense"\, v. t.
   To furnish with defenses; to fortify. [Obs.] [Written also
   {defence}.]

         Better manned and more strongly defensed. --Hales.

Source : WordNet®

defense
     n 1: (sports) the team that is trying to prevent the other team
          from scoring; "his teams are always good on defense"
          [syn: {defence}, {defending team}] [ant: {offense}, {offense}]
     2: military action or resources protecting a country against
        potential enemies; "they died in the defense of
        Stalingrad"; "they were developed for the defense program"
        [syn: {defence}, {defensive measure}]
     3: the defendant and his legal advisors collectively; "the
        defense called for a mistrial" [syn: {defence}, {defense
        team}, {defense lawyers}] [ant: {prosecution}]
     4: protection from harm; "sanitation is the best defense
        against disease" [syn: {defence}]
     5: a structure used for defense; "the artillery battered down
        the defenses" [syn: {defensive structure}, {defence}]
     6: the speech act of answering an attack on your assertions;
        "his refutation of the charges was short and persuasive";
        "in defense he said the other man started it" [syn: {refutation},
         {defence}]
     7: the justification for some act or belief; "he offered a
        persuasive defense of the theory" [syn: {defence}, {vindication}]
     8: a defendant's answer or plea denying the truth of the
        charges against him; "he gave evidence for the defense"
        [syn: {defence}, {denial}, {demurrer}] [ant: {prosecution}]
     9: an organization of defenders that provides resistance
        against attack; "he joined the defense against invasion"
        [syn: {defence}, {defense force}, {defence force}]
     10: the federal department responsible for safeguarding national
         security of the UnitedStates; created in 1947 [syn: {Department
         of Defense}, {Defense Department}, {United States
         Department of Defense}, {DoD}]
     11: (psychiatry) an unconscious process that tries to reduce the
         anxiety associated with instinctive desires [syn: {defense
         mechanism}, {defense reaction}, {defence mechanism}, {defence
         reaction}, {defence}]