The Collaborative International Dictionary of English v.0.48:

Truculent \Tru"cu*lent\, a. [L. truculentus, fr. trux, gen.
   trucis, wild, fierce: cf. F. truculent.]
   1. Fierce; savage; ferocious; barbarous; as, the truculent
      inhabitants of Scythia. --Ray.
      [1913 Webster]

   2. Cruel; destructive; ruthless.
      [1913 Webster]

            More or less truculent plagues.       --Harvey.
      [1913 Webster]

WordNet (r) 3.0 (2006):

truculent
    adj 1: defiantly aggressive; "a truculent speech against the new
           government"

Moby Thesaurus II by Grady Ward, 1.0:

128 Moby Thesaurus words for "truculent":
   Draconian, Tartarean, abrupt, aggressive, animal, antagonistic,
   anthropophagous, atrocious, bad-tempered, barbaric, barbarous,
   battling, bearish, beastly, bellicose, belligerent, bestial,
   bloodthirsty, bloody, bloody-minded, bluff, blunt, brash,
   browbeating, brusque, brutal, brutalized, brute, brutish, bullying,
   cannibalistic, cavalier, chauvinist, chauvinistic, churlish,
   combative, contentious, contumelious, cowing, cruel, cruel-hearted,
   crusty, curt, demoniac, demoniacal, devilish, diabolic, enemy,
   fell, feral, ferocious, fiendish, fiendlike, fierce, fighting,
   frightening, full of fight, grim, gruff, harsh, hawkish, hellish,
   hostile, ill-tempered, infernal, inhuman, inhumane, inimical,
   intimidating, invective, jingo, jingoish, jingoist, jingoistic,
   martial, militant, militaristic, military, murderous, nasty,
   obstreperous, offensive, opprobrious, pugnacious, quarrelsome,
   rough, rude, ruthless, saber-rattling, sadistic, sanguinary,
   sanguineous, satanic, savage, scathing, scrappy, scurrile,
   scurrilous, severe, sharkish, sharp, short, slavering, snippy,
   soldierlike, soldierly, subhuman, sullen, surly, terrifying,
   terrorizing, trigger-happy, unchristian, uncivilized, unfriendly,
   unhuman, unpacific, unpeaceable, unpeaceful, unpleasant, vicious,
   violent, virulent, vituperative, warlike, warmongering, warring,
   wolfish