A twinstick or duopoly (broadcasting) operation to which a third local station under the same common ownership has been added. If programming (and not just ownership) is the same across three stations in the same market, the cluster is not a triopoly but a trimulcast.
Topics referred to by the same term
This disambiguation page lists articles associated with the title Triopoly. If an internal link incorrectly led you here, you may wish to change the link to point directly to the intended article.