The Collaborative International Dictionary of English v.0.48:

Precedent \Prec"e*dent\, n.
   1. Something done or said that may serve as an example to
      authorize a subsequent act of the same kind; an
      authoritative example.
      [1913 Webster]

            Examples for cases can but direct as precedents
            only.                                 --Hooker.
      [1913 Webster]

   2. A preceding circumstance or condition; an antecedent;
      hence, a prognostic; a token; a sign. [Obs.]
      [1913 Webster]

   3. A rough draught of a writing which precedes a finished
      copy. [Obs.] --Shak.
      [1913 Webster]

   4. (Law) A judicial decision which serves as a rule for
      future determinations in similar or analogous cases; an
      authority to be followed in courts of justice; forms of
      proceeding to be followed in similar cases. --Wharton.
      [1913 Webster]

   Syn: Example; antecedent.

   Usage: Precedent, Example. An example in a similar case
          which may serve as a rule or guide, but has no
          authority out of itself. A precedent is something
          which comes down to us from the past with the sanction
          of usage and of common consent. We quote examples in
          literature, and precedents in law.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Precedent \Pre*ced"ent\, a. [L. praecedens, -entis, p. pr. of
   praecedere: cf. F. pr['e]c['e]dent. See Precede.]
   Going before; anterior; preceding; antecedent; as, precedent
   services. --Shak. "A precedent injury." --Bacon.
   [1913 Webster]

   Condition precedent (Law), a condition which precede the
      vesting of an estate, or the accruing of a right.
      [1913 Webster]

WordNet (r) 3.0 (2006):

precedent
    adj 1: preceding in time, order, or significance
    n 1: an example that is used to justify similar occurrences at a
         later time [syn: precedent, case in point]
    2: (civil law) a law established by following earlier judicial
       decisions [syn: case law, precedent, common law]
    3: a system of jurisprudence based on judicial precedents rather
       than statutory laws; "common law originated in the unwritten
       laws of England and was later applied in the United States"
       [syn: common law, case law, precedent]
    4: a subject mentioned earlier (preceding in time)

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "precedent":
   action, ancestor, announcer, antecedent, anterior, antetype,
   antitype, archetype, avant-garde, award, bellwether, biotype,
   buccinator, bushwhacker, classic example, condemnation,
   consideration, criterion, decision, decree, deliverance,
   determination, diagnosis, dictum, doom, epitome, example, exemplar,
   explorer, finding, forebear, foregoer, foregoing, forerunner,
   former, front runner, frontiersman, fugleman, fugler, genotype,
   groundbreaker, guide, harbinger, herald, imitatee, innovator, lead,
   lead runner, leader, messenger, mirror, model, order, original,
   paradigm, past, pathfinder, pattern, pioneer, point, precursor,
   predecessor, premise, previous, prior, prognosis, pronouncement,
   prototype, representative, resolution, rule, ruling, scout,
   sentence, standard, stormy petrel, trailblazer, trailbreaker, type,
   type species, type specimen, urtext, vanguard, vaunt-courier,
   verdict, voortrekker, yardstick



The Devil's Dictionary (1881-1906):

PRECEDENT, n.  In Law, a previous decision, rule or practice which, in
the absence of a definite statute, has whatever force and authority a
Judge may choose to give it, thereby greatly simplifying his task of
doing as he pleases.  As there are precedents for everything, he has
only to ignore those that make against his interest and accentuate
those in the line of his desire.  Invention of the precedent elevates
the trial-at-law from the low estate of a fortuitous ordeal to the
noble attitude of a dirigible arbitrament.


The Devil's Dictionary (1881-1906):

PRECEDENT, n.  In Law, a previous decision, rule or practice which, in
the absence of a definite statute, has whatever force and authority a
Judge may choose to give it, thereby greatly simplifying his task of
doing as he pleases.  As there are precedents for everything, he has
only to ignore those that make against his interest and accentuate
those in the line of his desire.  Invention of the precedent elevates
the trial-at-law from the low estate of a fortuitous ordeal to the
noble attitude of a dirigible arbitrament.