The Collaborative International Dictionary of English v.0.48:
Sacristy \Sac"ris*ty\, n.; pl. Sacristies. [F. sacristie, LL. sacristia, fr. L. sacer. See Sacred.] An apartment in a church where the sacred utensils, vestments, etc., are kept; a vestry. [1913 Webster]WordNet (r) 3.0 (2006):
sacristy n 1: a room in a church where sacred vessels and vestments are kept or meetings are held [syn: vestry, sacristy]