Metroliner (n.)

mid-14c., "bishop having general superintendency over other bishops of his province," from Late Latin metropolitanus, from Greek metropolis "mother city" (from which others have been colonized), parent state of a colony," also "capital city," and, in Ecclesiastical Greek, "see of a metropolitan bishop," from meter "mother" (see mother (n.1)) + polis "city" (see polis).

In the early church, the bishop of a municipal capital of a province or eparchy, who had general superintendence over the bishops in his province. In modern Catholic use, an archbishop who has bishops under his authority; in the Greek church still the bishop of a municipal capital of a province, ranking above an archbishop.