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definitions

book of hours

or Book of Hours

noun
  1. a book containing the prescribed order of prayers, readings from Scripture, and rites for the canonical hours.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for book of hours

book of hours

noun
  1. (often capitals) a book used esp in monasteries during the Middle Ages that contained the prayers and offices of the canonical hours
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