The Collaborative International Dictionary of English v.0.48:

Pugnacious \Pug*na"cious\, a. [L. pugnax, -acis, fr. pugnare to
   fight. Cf. Pugilism, Fist.]
   Disposed to fight; inclined to fighting; quarrelsome;
   fighting. --Pug*na"cious*ly, adv. -- Pug*na"cious*ness,
   n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pugnacious
    adj 1: tough and callous by virtue of experience [syn: hard-
           bitten, hard-boiled, pugnacious]
    2: ready and able to resort to force or violence; "pugnacious
       spirits...lamented that there was so little prospect of an
       exhilarating disturbance"- Herman Melville; "they were rough
       and determined fighting men" [syn: pugnacious, rough]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "pugnacious":
   aggressive, antagonistic, battling, bellicose, belligerent,
   bickering, bloodthirsty, bloody, bloody-minded, brawling,
   chauvinist, chauvinistic, combative, contentious, disputatious,
   divisive, enemy, eristic, factional, factious, ferocious, fierce,
   fight, fighting, full of fight, hawkish, hostile, inimical,
   irascible, irritable, jingo, jingoish, jingoist, jingoistic,
   litigious, martial, militant, militaristic, military, offensive,
   partisan, polarizing, polemic, pushing, pushy, quarrelsome,
   rebellious, saber-rattling, sanguinary, sanguineous, savage,
   scrappy, self-assertive, shrewish, soldierlike, soldierly,
   trigger-happy, truculent, unfriendly, unpacific, unpeaceable,
   unpeaceful, warlike, warmongering, warring, wrangling