1. 
[syn: contentious, combative, disputatious, disputative, litigious]
2.  involving or likely to cause controversy; 
- Example: "a central and contentious element of the book"- Tim W.Ferfuson
The Collaborative International Dictionary of English v.0.48:
Contentious \Con*ten"tious\, a. [L. contentiosus: cf. F.
   contentieux.]
   1. Fond of contention; given to angry debate; provoking
      dispute or contention; quarrelsome.
      [1913 Webster]
            Despotic and contentious temper.      --Macaulay.
      [1913 Webster]
   2. Relating to contention or strife; involving or
      characterized by contention. --Spenser.
      [1913 Webster]
            More cheerful, though not less contentious, regions.
                                                  --Brougham.
      [1913 Webster]
   3. (Law) Contested; litigated; litigious; having power to
      decide controversy.
      [1913 Webster]
   Contentious jurisdiction (Eng. Eccl. Law), jurisdiction
      over matters in controversy between parties, in
      contradistinction to voluntary jurisdiction, or that
      exercised upon matters not opposed or controverted.
   Syn: Quarrelsome; pugnacious; dissentious; wrangling;
        litigious; perverse; peevish. -- Con*ten"tious*ly,
        adv. -- Con*ten"tious*ness, n.
        [1913 Webster]
WordNet (r) 3.0 (2006):
contentious
    adj 1: inclined or showing an inclination to dispute or
           disagree, even to engage in law suits; "a style described
           as abrasive and contentious"; "a disputatious lawyer"; "a
           litigious and acrimonious spirit" [syn: contentious,
           combative, disputatious, disputative, litigious]
    2: involving or likely to cause controversy; "a central and
       contentious element of the book"- Tim W.Ferfuson
Moby Thesaurus II by Grady Ward, 1.0:
67 Moby Thesaurus words for "contentious":
   aggravating, aggravative, aggressive, annoying, antagonistic,
   argumental, argumentative, battling, bellicose, belligerent,
   bloodthirsty, bloody, bloody-minded, cat-and-dog, cat-and-doggish,
   chauvinist, chauvinistic, combative, controversial, dialectic,
   disputatious, enemy, eristic, exasperating, exasperative,
   ferocious, fierce, fighting, full of fight, hawkish, hostile,
   ill-humored, inimical, irritating, jingo, jingoish, jingoist,
   jingoistic, litigious, logomachic, martial, militant, militaristic,
   military, offensive, pilpulistic, polemic, pro and con,
   provocative, pugnacious, quarrelsome, saber-rattling, sanguinary,
   sanguineous, savage, scrappy, soldierlike, soldierly,
   trigger-happy, truculent, unfriendly, unpacific, unpeaceable,
   unpeaceful, warlike, warmongering, warring