The Collaborative International Dictionary of English v.0.48:

Litigation \Lit`i*ga"tion\, n. [L. litigatio, fr. litigare to
   dispute, litigate; lis, litis, dispute, lawsuit (OL. stlis) +
   agere to carry on. See Agent.]
   The act or process of litigating; a suit at law; a judicial
   contest.
   [1913 Webster]

WordNet (r) 3.0 (2006):

litigation
    n 1: a legal proceeding in a court; a judicial contest to
         determine and enforce legal rights [syn: litigation,
         judicial proceeding]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "litigation":
   Kilkenny cats, action, altercation, apologetics, apologia, apology,
   argument, argumentation, bicker, bickering, case, casuistry,
   cat-and-dog life, cause, cause in court, combat, conflict,
   contention, contentiousness, contest, contestation, controversy,
   cut and thrust, debate, defense, disputation, dispute, enmity,
   fighting, flyting, hassle, hostility, hubbub, judicial process,
   lawsuit, legal action, legal case, legal proceedings,
   legal process, legal remedy, logomachy, paper war, passage of arms,
   polemic, polemics, proceedings, prosecution, quarrel, quarreling,
   quarrelsomeness, rhubarb, scrapping, set-to, squabbling, strife,
   struggle, suit, suit at law, verbal engagement, war, war of words,
   warfare, words, wrangling



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

LITIGATION. A contest authorized by law, in a court of justice, for the
purpose of enforcing a right.
     2. In order to prevent injustice, courts of equity will restrain a
party from further litigation, by a writ of injunction; for example, after
two verdicts on trials at bar, in favor of the plaintiff, a perpetual
injunction was decreed. Str. 404. And not only between two individuals will
a court of equity grant this relief, as in the above case of several
ejectments, but also, when one general legal right, as a right of fishery,
is claimed against several, distinct persons, in which case there would be
no end of bringing actions, since each action would only bind the particular
right in question, between the plaintiff and defendant in such action,
without deciding the general right claimed. 2 Atk. 484; 2 Ves. jr. 587. Vide
Circuity of Actions.



The Devil's Dictionary (1881-1906):

LITIGATION, n.  A machine which you go into as a pig and come out of
as a sausage.