noun

1. A rejection; a vote against admitting someone.

2. A black ball used to indicate such a negative vote.

   “Regardless how many other people may have voted to approve a candidate for membership, a single blackball will reject the candidate.”

3. A kind of large black sweet; a niggerball.

verb

1. To vote against, especially in an exclusive organization.

   “If you're not from a moneyed, well-connected family, you can count on getting blackballed from the fraternity.”

2. To ostracize.

Synonyms: blacklist, send to Coventry