The Collaborative International Dictionary of English v.0.48:

Plurality \Plu*ral"i*ty\, n.; pl. pluralities. [L. pluralitas:
   cf. F. pluralit['e].]
   1. The state of being plural, or consisting of more than one;
      a number consisting of two or more of the same kind; as, a
      plurality of worlds; the plurality of a verb.
      [1913 Webster]

   2. The greater number; a majority; also, the greatest of
      several numbers; in elections, the excess of the votes
      given for one candidate over those given for another, or
      for any other, candidate. When there are more than two
      candidates, the one who receives the plurality of votes
      may have less than a majority. See Majority.
      [1913 Webster]

            Take the plurality of the world, and they are
            neither wise nor good.                --L'Estrange.
      [1913 Webster]

   3. (Eccl.) See Plurality of benefices, below.
      [1913 Webster]

   Plurality of benefices (Eccl.), the possession by one
      clergyman of more than one benefice or living. Each
      benefice thus held is called a plurality. [Eng.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

plurality
    n 1: the state of being plural; "to mark plurality, one language
         may add an extra syllable to the word whereas another may
         simply change the vowel in the existing final syllable"
    2: a large indefinite number; "a battalion of ants"; "a
       multitude of TV antennas"; "a plurality of religions" [syn:
       battalion, large number, multitude, plurality,
       pack]
    3: (in an election with more than 2 options) the number of votes
       for the candidate or party receiving the greatest number (but
       less that half of the votes) [syn: plurality, relative
       majority]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "plurality":
   a mass of, a world of, army, best part, better part, bevy, body,
   bulk, bunch, cloud, clutter, covey, essence, flight, flock, flocks,
   generality, gist, gravamen, hail, hive, host, jam, large amount,
   legion, lots, main body, major part, majority, many, mass,
   masses of, meat, mob, more than half, most, muchness, multitude,
   nest, numbers, pack, preponderance, preponderancy, quantities,
   quite a few, rout, ruck, scores, shoal, substance, swarm,
   the greatest number, throng, thrust, tidy sum, worlds of



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

PLURALITY, government. The greater number of votes given at an election; it
is distinguished from a majority, (q.v.) which is a plurality of all the
votes which might have been given; though in common parlance majority is
used in the sense here given to plurality.