any one of the letters from A to G used in church calendars to mark the Sundays throughout any particular year, serving primarily to aid in determining the date of Easter.
Origin of dominical letter
First recorded in 1570–80
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Christianity any one of the letters A to G as used to denote Sundays in a given year in order to determine the church calendar
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012