Triduum
A period of three days of preparation for a feast day. The term is most frequently used for Maundy Thursday, Good Friday, and Holy Saturday, the three days prior to Easter Sunday that are the concluding days of Holy Week, also known as the Easter Triduum. Other usage for the Easter Triduum reckons the days from the evening of Maundy Thursday through the evening of Easter Day. The term may indicate any three-day period of preparation for a feast.
Glossary definitions provided courtesy of Church Publishing Incorporated, New York, NY,(All Rights reserved) from “An Episcopal Dictionary of the Church, A User Friendly Reference for Episcopalians,” Don S. Armentrout and Robert Boak Slocum, editors.