Any of various arrangements in which payment is rendered in exchange for a specific right, service, or privilege, often one for which a charge would not always be expected, especially:
a. one in which participants pay to take part in a sport or game.
b. one in which entertainers, performers, or artists pay for public exposure of their work.
c. one in which political influence or appointments are given in exchange for contributions to a party or candidate.
d. one in which producers or distributors pay for favorable placements of their products.