BLACKBALL

A rejection; a vote against admitting someone.

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."

A kind of large black sweet; a niggerball.

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."

To ostracize.