That’s the informal slang for those who are changing their church affiliation from Roman Catholic to attending an Anglican/Episcopal church. Those headed in the opposite direction are said to be “crossing the Rubicon,” which refers to a famous boundary river in the ancient Roman empire.
It’s not surprising that Episcopal churches benefit from departing Catholics. Articles on departing Catholics in NCR and Commonweal interview Episcopal priests from different parts of the country who estimate that upwards of 50% or more of their new members are ex-RC. That certainly matches with our informal observation at St Paul’s Cathedral, where lots of the congregants are ex-Roman. We’ve even met a couple of former priests.
As Father Steve is fond of reminding us, all three of the priests at St Nicholas were originally ordained in the Roman Catholic Church and left for the Episcopal church, each for compelling personal reasons. And all three attended the same Catholic seminary, too. About half of our members originally started out as Catholics, which pegs us as a fairly average sample.