A day set aside for fasting and prayer WordNet 3.0 & Open English WordNet

Ember Days are quarterly periods of prayer and fasting in the liturgical calendar of Western Christian churches. Wikipedia

Fasting days within Western Christian churches Wikipedia Disambiguation

Any of the three days within the same week, four separate sets of which occur roughly equidistant in the circuit of the year, that are set aside for fasting and prayer. In Western Christianity they are usually the Wednesday, Friday, and Saturday following the first Sunday in Lent, Whitsunday, Holy Cross Day (14 September), and Saint Lucy's Day (13 December). Wiktionary

Any of the three days within the same week, four separate sets of which occur roughly equidistant in the circuit of the year, set aside for fasting and prayer. Wiktionary (translation)