Medieval European Fantasy, which possesses attributes stereotypically associated with Christianity (especially Roman Catholicism) -- such as priestly vestements, nuns and their habits, confessionals, the designs of houses of worship, and crosses -- but which centers on a deity other than the Christian God, like an animistic spirit or pagan-flavored god.One example, particularly annoying to me, was of course the Religion of the Seven from GAME OF THRONES.
Much of the time, in order to finalize the separation, the deity worshipped is a goddess, as opposed to the male deity of most real-life religions. In these cases, they are usually just called "the Goddess". (This may be based off the common use by neopagan religions of this term to denote the main female deity.)
The Faith of the Seven, the predominant religion on the continent of Westeros in George R.R. Martin's A Song Of Ice And Fire series, is closely modeled after Roman Catholicism, complete with analogs to the Trinity (the Father, Mother, Warrior, Maid, Smith, Crone, and Stranger being aspects of the same deity), monastic orders, dormant military orders, and a Pope (the High Septon).
This is also why the abbreviation C.E. ("Common Era") in place of A.D. bothers me. The faux people are trying to use a faux calendar system without actually giving credit to the Church That None Dare Name. It is merely a slap in the face of Christians, an insolent attempt to take their calendar without admitting you are taking something not yours. Who was born on the year 1 C.E. from which you date your years, oh ye people who follow the Common Era? Who was born then? Dragon Crystal Jesus?
Yes, a useful term.