Real Dictionary

sacristy
countable noun: A sacristy is the room in a church where the priest or minister changes into their official clothes and where holy objects are kept.

sacristy in American English
a room in a church, usually adjoining the sanctuary, where the sacred vessels, vestments, etc. are kept; vestry
noun: an apartment in or a building connected with a church or a religious house, in which the sacred vessels, vestments, etc., are kept

sacristy in British English
noun: a room attached to a church or chapel where the sacred vessels, vestments, etc, are kept and where priests attire themselves