noun, feminine/py.nɛz də sa.kʁis.ti/plural: punaises de sacristie
a Holy Mary, a zealot, a God botherer, a Jesus freak, a Bible thumper (an excessively pious woman, a woman who spends a lot of a time in the church)
Synonyms: cul-bénit, grenouille de bénitier
Literally, “vestry stinkbug”.