The Collaborative International Dictionary of English v.0.48:

Antecedent \An`te*ced"ent\, a. [L. antecedens, -entis, p. pr. of
   antecedere: cf. F. ant['e]c['e]dent.]
   1. Going before in time; prior; anterior; preceding; as, an
      event antecedent to the Deluge; an antecedent cause.
      [1913 Webster]

   2. Presumptive; as, an antecedent improbability.
      [1913 Webster]

   Syn: Prior; previous; foregoing.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Antecedent \An`te*ced"ent\, n. [Cf. F. ant['e]c['e]dent.]
   1. That which goes before in time; that which precedes.
      --South.
      [1913 Webster]

            The Homeric mythology, as well as the Homeric
            language, has surely its antecedents. --Max Miller.
      [1913 Webster]

   2. One who precedes or goes in front. [Obs.]
      [1913 Webster]

            My antecedent, or my gentleman usher. --Massinger.
      [1913 Webster]

   3. pl. The earlier events of one's life; previous principles,
      conduct, course, history. --J. H. Newman.
      [1913 Webster]

            If the troops . . . prove worthy of their
            antecedents, the victory is surely ours. --Gen. G.
                                                  McClellan.
      [1913 Webster]

   4. (Gram.) The noun to which a relative refers; as, in the
      sentence "Solomon was the prince who built the temple,"
      prince is the antecedent of who.
      [1913 Webster]

   5. (Logic)
      (a) The first or conditional part of a hypothetical
          proposition; as, If the earth is fixed, the sun must
          move.
      (b) The first of the two propositions which constitute an
          enthymeme or contracted syllogism; as, Every man is
          mortal; therefore the king must die.
          [1913 Webster]

   6. (Math.) The first of the two terms of a ratio; the first
      or third of the four terms of a proportion. In the ratio
      a:b, a is the antecedent, and b the consequent.
      [1913 Webster]

WordNet (r) 3.0 (2006):

antecedent
    adj 1: preceding in time or order [ant: subsequent]
    n 1: someone from whom you are descended (but usually more
         remote than a grandparent) [syn: ancestor, ascendant,
         ascendent, antecedent, root] [ant: descendant,
         descendent]
    2: a preceding occurrence or cause or event
    3: anything that precedes something similar in time; "phrenology
       was an antecedent of modern neuroscience" [syn: antecedent,
       forerunner]
    4: the referent of an anaphor; a phrase or clause that is
       referred to by an anaphoric pronoun

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "antecedent":
   agency, ancestor, ancestors, announcer, antecede, antecedents,
   antedate, anterior, anticipatory, ascendant, ascendants,
   avant-garde, base, basis, bellwether, buccinator, bushwhacker,
   call, causation, cause, cause and effect, chief, ci-devant,
   determinant, determinative, earlier, early, elder, elders, element,
   etiology, exordial, explorer, factor, fathers, first, fore,
   forebear, forebears, forefather, forefathers, foregoer, foregoing,
   foremost, forerun, forerunner, former, front runner, frontiersman,
   fugleman, grandfathers, grandparents, ground, groundbreaker,
   grounds, guide, harbinger, heading, headmost, herald, inaugural,
   initiatory, innovator, instrumentality, lead runner, leader,
   leading, means, messenger, occasion, older, pace, past, pathfinder,
   patriarchs, pioneer, point, precedent, preceding, precessional,
   precurrent, precursor, precursory, predate, predecessor,
   predecessors, preexistent, prefatory, preliminary, preludial,
   prelusive, premise, preparatory, prevenient, previous, prime,
   primogenitor, principle, prior, proemial, progenitor, progenitors,
   propaedeutic, prototype, reason, scout, senior, stimulus,
   stormy petrel, trailblazer, trailbreaker, vanguard, vaunt-courier,
   voortrekker



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

ANTECEDENT. Something that goes before. In the construction of laws,
agreements, and the like, reference is always to be made to the last
antecedent; ad proximun antecedens fiat relatio. But not only the
antecedents but the subsequent clauses of the instrument must be considered:
Ex antecedentibus et consequentibus fit optima interpretatio.