An officer in Christian churches appointed to perform certain subordinate duties varying in different communions. In the Roman Catholic and Episcopal churches, a person admitted to the lowest order in the ministry, subordinate to the bishops and priests. In Presbyterian churches, he is subordinate to the minister and elders, and has charge of certain duties connected with the communion service and the care of the poor. In Congregational churches, he is subordinate to the pastor, and has duties as in the Presbyterian church.
- A cleric ranking just below a priest in the Anglican, Eastern Orthodox, and Roman Catholic churches.
- A Protestant layperson who assists the minister in various functions.
- Used as a title prefixed to the surname of such a person: Deacon Brown.