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n. A book or list of lections to be read at church services during the year.

n. A book or listing that contains a collection of readings for Christian worship.

n. A book, or a list, of lections, for reading in divine service.

n. A book for use in religious worship, containing portions of Scripture to be read for particular days: same as epistolary.

n. A table of lessons or portions of Scripture for particular days.

"This wider signification is, however, perhaps the less usual, and in practice the term lectionary is more commonly used to denote one of two things: (1) the book containing the collection of Scriptural readings which are chanted by the deacon, subdeacon, or a lector during Mass;"

Wikipedia article on Lectionaries   

lection    lector