The Collaborative International Dictionary of English v.0.48:

Fight \Fight\ (f[imac]t), v. i. [imp. & p. p. Fought
   (f[add]t); p. pr. & vb. n. Fighting.] [OE. fihten, fehten,
   AS. feohtan; akin to D. vechten, OHG. fehtan, G. fechten, Sw.
   f[aum]kta, Dan. fegte, and perh. to E. fist; cf. L. pugnare
   to fight, pugnus fist.]
   1. To strive or contened for victory, with armies or in
      single combat; to attempt to defeat, subdue, or destroy an
      enemy, either by blows or weapons; to contend in arms; --
      followed by with or against.
      [1913 Webster]

            You do fight against your country's foes. --Shak.
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            To fight with thee no man of arms will deign.
                                                  --Milton.
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   2. To act in opposition to anything; to struggle against; to
      contend; to strive; to make resistance.
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   To fight shy, to avoid meeting fairly or at close quarters;
      to keep out of reach.
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The Collaborative International Dictionary of English v.0.48:

Fighting \Fight"ing\, a.
   1. Qualified for war; fit for battle.
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            An host of fighting men.              --2 Chron.
                                                  xxvi. 11.
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   2. Occupied in war; being the scene of a battle; as, a
      fighting field. --Pope.
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   A fighting chance, one dependent upon the issue of a
      struggle. [Colloq.]

   Fighting crab (Zool.), the fiddler crab.

   Fighting fish (Zool.), a remarkably pugnacious East Indian
      fish (Betta pugnax), reared by the Siamese for
      spectacular fish fights.
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WordNet (r) 3.0 (2006):

fighting
    adj 1: engaged in or ready for military or naval operations; "on
           active duty"; "the platoon is combat-ready"; "review the
           fighting forces" [syn: active, combat-ready,
           fighting(a)]
    n 1: the act of fighting; any contest or struggle; "a fight
         broke out at the hockey game"; "there was fighting in the
         streets"; "the unhappy couple got into a terrible scrap"
         [syn: fight, fighting, combat, scrap]

Moby Thesaurus II by Grady Ward, 1.0:

125 Moby Thesaurus words for "fighting":
   Chinese boxing, Kilkenny cats, aggressive, all-out war,
   altercation, antagonistic, appeal to arms, argument, armed combat,
   armed conflict, attack, battle, battling, bellicose, belligerence,
   belligerency, belligerent, bickering, bloodshed, bloodthirsty,
   bloody, bloody-minded, bout, boxing, boxing match,
   cat-and-dog life, chauvinist, chauvinistic, close fighting, combat,
   combative, conflict, contending, contention, contentious,
   contentiousness, contest, contestant, contestation, contesting,
   controversy, cut and thrust, debate, disputant, disputation,
   dispute, enemy, enmity, ferocious, fierce, fisticuffs,
   full of fight, hawkish, hostile, hostilities, hostility, hot war,
   infighting, inimical, jingo, jingoish, jingoist, jingoistic,
   la guerre, litigation, logomachy, martial, might of arms, militant,
   militaristic, military, military operations, offensive,
   open hostilities, open war, paper war, polemic, prizefight,
   prizefighting, pugilism, pugnacious, quarrel, quarreling,
   quarrelsome, quarrelsomeness, resort to arms, saber-rattling,
   sanguinary, sanguineous, savage, savate, scrapping, scrappy,
   shadowboxing, shooting war, soldierlike, soldierly, spar,
   squabbling, state of war, strife, striving, struggle, struggling,
   the clinches, the fights, the ring, the sword, total war,
   trigger-happy, truculent, unfriendly, unpacific, unpeaceable,
   unpeaceful, war, war of words, warfare, warlike, warmaking,
   warmongering, warring, wartime, words, wrangling