The Collaborative International Dictionary of English v.0.48:

Militant \Mil"i*tant\, a. [L. militans, -antis, p. pr. of
   militare to be soldier: cf. F. militant. See Militate.]
   Engaged in warfare; fighting; combating; serving as a
   soldier. -- Mil"i*tant*ly, adv.
   [1913 Webster]

         At which command the powers militant . . .
         Moved on in silence.                     --Milton.
   [1913 Webster]

   Church militant, the Christian church on earth, which is
      supposed to be engaged in a constant warfare against its
      enemies, and is thus distinguished from the church
      triumphant, in heaven.
      [1913 Webster]

WordNet (r) 3.0 (2006):

militant
    adj 1: disposed to warfare or hard-line policies; "militant
           nations"; "hawkish congressman"; "warlike policies" [syn:
           militant, hawkish, warlike]
    2: showing a fighting disposition; "highly competitive sales
       representative"; "militant in fighting for better wages for
       workers"; "his self-assertive and ubiquitous energy" [syn:
       competitive, militant]
    3: engaged in war; "belligerent (or warring) nations" [syn:
       belligerent, militant, war-ridden, warring]
    n 1: a militant reformer [syn: militant, activist]

Moby Thesaurus II by Grady Ward, 1.0:

165 Moby Thesaurus words for "militant":
   active, activist, activistic, aggressive, aggressor, alive,
   animated, antagonistic, assertive, at war, ball of fire, battler,
   battling, beaver, bellicose, belligerent, belted knight, bickerer,
   big-time operator, blade, bloodthirsty, bloody, bloody-minded,
   bouncing, bouncy, bravo, brawler, breezy, brisk, bubbly, bully,
   bullyboy, bustler, busy bee, chauvinist, chauvinistic, chipper,
   combatant, combative, competitor, contender, contentious,
   contestant, disputant, doer, duelist, eager beaver, ebullient,
   effervescent, embattled, enemy, energetic, enforcer, enthusiast,
   fencer, ferocious, feuder, fierce, fighter, fighting,
   fighting cock, foilsman, frisky, full of fight, full of go,
   full of life, full of pep, gamecock, gladiator, go-getter, goon,
   gorilla, hatchet man, hawkish, hood, hoodlum, hooligan, hostile,
   human dynamo, hustler, inimical, jingo, jingoish, jingoist,
   jingoistic, jouster, knight, live, live wire, lively,
   man of action, man of deeds, martial, mercurial, militaristic,
   military, new broom, offensive, operator, peppy, perky, pert,
   plug-ugly, political activist, powerhouse, pugnacious, pushful,
   pushing, pushy, quarreler, quarrelsome, quicksilver, rioter, rival,
   rough, rowdy, ruffian, saber-rattling, sabreur, sanguinary,
   sanguineous, savage, scrapper, scrappy, scuffler, self-assertive,
   smacking, snappy, soldier, soldierlike, soldierly, spanking,
   spirited, sprightly, spry, squabbler, strong arm, strong-arm man,
   strong-armer, struggler, swashbuckler, sword, swordplayer,
   swordsman, take-charge guy, thug, tilter, tough, trigger-happy,
   truculent, tussler, unfriendly, unpacific, unpeaceable, unpeaceful,
   up in arms, vivacious, warlike, warmongering, warring, warrior,
   wheeler-dealer, winner, wrangler, zingy