someone who assists a priest or minister in a liturgical service; a cleric ordained in the highest of the minor orders in the Roman Catholic Church but not in the Anglican Church or the Eastern Orthodox Churches
One who has received the highest of the four minor orders in the Catholic Church, being ordained to carry the wine, water and lights at Mass.
The word comes from the Ancient Greek akólouthos, meaning "follower" or "attendant." It entered English through Middle English and Old French.