The Collaborative International Dictionary of English v.0.48:

Blackball \Black"ball`\, n.
   1. A composition for blacking shoes, boots, etc.; also, one
      for taking impressions of engraved work.
      [1913 Webster]

   2. A ball of black color, esp. one used as a negative in
      voting; -- in this sense usually two words.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Blackball \Black"ball`\, v. t. [imp. & p. p. Blackballed; p.
   pr. & vb. n. Blackballing.]
   1. To vote against, by putting a black ball into a ballot
      box; to reject or exclude, as by voting against with black
      balls; to ostracize.
      [1913 Webster]

            He was blackballed at two clubs in succession.
                                                  --Thackeray.
      [1913 Webster]

   2. To blacken (leather, shoes, etc.) with blacking.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blackball
    n 1: the act of excluding someone by a negative vote or veto
         [syn: barring, blackball]
    v 1: expel from a community or group [syn: banish, ban,
         ostracize, ostracise, shun, cast out, blackball]
    2: vote against; refuse to endorse; refuse to assent; "The
       President vetoed the bill" [syn: veto, blackball,
       negative]

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "blackball":
   ban, banish, banishment, blackballing, blacklist, boycott,
   boycottage, cast out, categorically reject, complaint, cut, deport,
   dim view, disagreement, disallow, disappointment, disapprobation,
   disapproval, disapprove, disapprove of, discontent,
   discontentedness, discontentment, disenchantment, disesteem,
   disfavor, disfellowship, disgruntlement, disillusion,
   disillusionment, displeasure, disrespect, dissatisfaction, dissent,
   dissent from, distaste, exclude, exclusion, excommunicate, exile,
   expatriate, expel, extradite, frown at, frown down, frown upon,
   fugitate, grimace at, indignation, look askance at,
   look black upon, low estimation, low opinion, not approve,
   not go for, not hear of, not hold with, object, object to,
   objection, oppose, opposition, opposure, ostracism, ostracization,
   ostracize, outlaw, proscribe, proscription, protest, reject,
   rejection, relegate, rusticate, say no to, send away, send down,
   send to Coventry, snub, spurn, take exception to, think ill of,
   think little of, thrust out, thumb down, thumbs-down, transport,
   unhappiness, view with disfavor