churched adj. having attended (Christian) religious services. (source: Double-Tongued Dictionary)
Further reading
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Growing up in the midwestern US, “the unchurched” was used in common small-town speech, although usually as a noun rather than as an adjective. I never recall hearing “churched” and it seemed very odd when I read it here. “Unchurched” was the opposite of “Christians” or of a denomination’s name, used the way Mormons say “Gentiles”
eta: This was in the 1950’s and 1960’s in Nebraska, Kansas, Illinois, Indiana.
Churched, as a word, implies that an action has taken place on the person in question. It is similar to saying a person has been “fixed” with a certain mind set according to the social institution known as the church.