any of the days in the quarterly three-day period of prayer and fasting (the Wednesday, Friday, and Saturday after the first Sunday in Lent, after Whitsunday, after Sept. 14, and after Dec. 13) observed in the Roman Catholic Church and other Western churches.
Origin of Ember day
before 1050; Middle English ymber day, Old English ymbrendæg, plural -dagas, equivalent to ymbryne recurrence (ymb(e) around + ryne a running) + dæg day
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for ember day
The following extracts from it refer to the Ember-day Fasts.St. Gregory and the Gregorian Music|E. G. P. Wyatt