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 Englishymber day,Old Englishymbrendæg, plural -dagas, equivalent to ymbryne recurrence (ymb(e) around + ryne a running) + dægday
RC ChurchAnglican Churchany of four groups of three days (always Wednesday, Friday, and Saturday) of prayer and fasting, the groups occurring after Pentecost, after the first Sunday of Lent, after the feast of St Lucy (Dec 13), and after the feast of the Holy Cross (Sept 14)
Word Origin for Ember days
Old English ymbrendǣg, from ymbren, perhaps from ymbryne a (recurring) period, from ymb around + ryne a course + dǣg day
Old English Ymbrendaeg, Ymbren, 12 days of the year (divided into four seasonal periods, hence Latin name quatuor tempora) set aside by the Church for fasting and prayers, from Old English ymbren "recurring," corruption of ymbryne "a circuit, revolution, course, anniversary," literally "a running around," from ymb "round" (cognate with Greek amphi, Latin ambo; see ambi-) + ryne "course, running" (see run (n.)). Perhaps influenced by a corruption of the Latin name (cf. German quatember).