1Roman Catholic Church
A person in a religious community whose duty is to remind members of that community of their vows, encourage observance of monastic rule, and to admonish or report transgressions.
In extended use, chiefly after W. G. Palgrave with reference to members of the religious police established in Riyadh, Saudi Arabia in the mid 19th cent.
2rare A zealot; especially a person who is excessively, immoderately, or fanatically devoted to a cause or ideal, especially a religious or political one.
Late Middle English (in an earlier sense). From (i) Middle French zelateur, (rare) zelatour, zelatur person who zealously promotes or furthers a cause, religion, etc., (depreciative) zealot.