triduum: Meaning and Definition of

trid•u•um

Pronunciation: (trij'-um, trid'y-), [key]
— n. Rom. Cath. Ch.
  1. a series of special religious observances over a three-day period, in preparation for a great feast.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.