The Collaborative International Dictionary of English v.0.48:

Litigious \Li*ti"gious\, a. [L. litigiosus, fr. litigium
   dispute, quarrel, fr. litigare: cf. F. litigieux. See
   Litigation.]
   1. Inclined to initiate lawsuits; given to the practice of
      contending in law; fond of litigation. " A pettifogging
      attorney or a litigious client." --Macaulay.
      [1913 Webster]

            Soldiers find wars, and lawyers find out still
            Litigious men, who quarrels move.     --Donne.
      [1913 Webster]

   2. Hence: Quarrelsome; contentious; argumentative.
      [1913 Webster]

   3. Subject to contention; disputable; controvertible;
      debatable; doubtful; precarious. --Shak.
      [1913 Webster]

            No fences, parted fields, nor marks, nor bounds,
            Distinguished acres of litigious grounds. --Dryden.
      [1913 Webster]

   4. Of or pertaining to legal disputes.
      [1913 Webster]

            Nor brothers cite to the litigious bar. --Young.
      [1913 Webster]

WordNet (r) 3.0 (2006):

litigious
    adj 1: of or relating to litigation
    2: 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]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "litigious":
   actionable, aggressive, argumental, argumentative, bellicose,
   belligerent, bickering, cat-and-dog, cat-and-doggish, causidical,
   combative, contentious, controversial, dialectic, disputatious,
   divisive, eristic, factional, factious, ill-humored, irascible,
   irritable, litigable, litigant, litigatory, logomachic, partisan,
   pilpulistic, polarizing, polemic, polemical, pro and con,
   pugnacious, quarrelsome, scrappy, shrewish, wrangling



Bouvier's Law Dictionary, Revised 6th Ed (1856):

LITIGIOUS. That which is the subject of a suit or action; that which is
contested in a court of justice. In another sense, litigious signifies a
disposition to sue; a fondness for litigation.