The Collaborative International Dictionary of English v.0.48:

Exclusion \Ex*clu"sion\, n. [L. exclusio: cf. F. exclusion. See
   Exclude.]
   1. The act of excluding, or of shutting out, whether by
      thrusting out or by preventing admission; a debarring;
      rejection; prohibition; the state of being excluded.
      [1913 Webster]

            His sad exclusion from the doors of bliss. --Milton.
      [1913 Webster]

            The exclusion of the duke from the crown of England
            and Ireland.                          --Hume.
      [1913 Webster]

   2. (Physiol.) The act of expelling or ejecting a fetus or an
      egg from the womb.
      [1913 Webster]

   3. Thing emitted. --Sir T. Browne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

exclusion
    n 1: the state of being excluded [ant: inclusion]
    2: the state of being excommunicated [syn: excommunication,
       exclusion, censure]
    3: a deliberate act of omission; "with the exception of the
       children, everyone was told the news" [syn: exception,
       exclusion, elision]
    4: the act of forcing out someone or something; "the ejection of
       troublemakers by the police"; "the child's expulsion from
       school" [syn: ejection, exclusion, expulsion,
       riddance]

Moby Thesaurus II by Grady Ward, 1.0:

145 Moby Thesaurus words for "exclusion":
   Eighteenth Amendment, Prohibition Party, Volstead Act, abjuration,
   abjurement, abscission, amputation, annihilation, ban, banishment,
   bar, blackball, blackballing, chucking, chucking out, complaint,
   contempt, contraband, contradiction, declination, declining,
   defrocking, degradation, demotion, denial, depluming, deportation,
   deprivation, despisal, despising, destruction, dim view,
   disagreement, disallowance, disappointment, disapprobation,
   disapproval, disbarment, discard, disclamation, discontent,
   discontentedness, discontentment, discounting, disenchantment,
   disesteem, disfavor, disfellowship, disgruntlement, disillusion,
   disillusionment, dismissal, disownment, displeasure, displuming,
   disregard, disrespect, dissatisfaction, dissent, distaste,
   ejection, elimination, embargo, eradication, eviction, exception,
   excision, excommunication, exile, expatriation, expulsion,
   extinction, extirpation, extradition, forbiddance, forbidden fruit,
   forbidding, fugitation, ignoring, index, index expurgatorius,
   index librorum prohibitorum, indignation, inhibition, injunction,
   interdict, interdiction, interdictum, law, lockout, low estimation,
   low opinion, mutilation, no-no, nonacceptance, nonapproval,
   nonconsideration, objection, omission, opposition, opposure,
   ostracism, ostracization, ouster, outlawing, outlawry, passing by,
   preclusion, prevention, prohibition, prohibitory injunction,
   proscription, protest, putting away, putting out, rebuff,
   recantation, refusal, rejection, relegation, removal, renouncement,
   repression, repudiation, repulse, rescission,
   restrictive covenants, riddance, ruling out, rustication, scouting,
   spurning, statute, stripping, sumptuary laws, suppression, taboo,
   throwing out, thumbs-down, transportation, turning out, unfrocking,
   unhappiness, zoning, zoning laws