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]