
1) Office of matins division 2) Psalter portion
Found on
https://www.crosswordclues.com/clue/nocturn

• (n.) An office of devotion, or act of religious service, by night. • (n.) One of the portions into which the Psalter was divided, each consisting of nine psalms, designed to be used at a night service. • (n.) An office of devotion, or act of religious service, by night. • (n.) One of the portions into which the Psalter was div...
Found on
http://thinkexist.com/dictionary/meaning/nocturn/
Noc'turn noun [ French
nocturne , from Latin
nocturnus . See
Nocturnal , and confer
Nocturne .]
1. An office of devotion, or act of religious service, by night.
2. One of the portions into which the Psalter was divided, each consisting of nine psalms, desig...
Found on
http://www.encyclo.co.uk/webster/N/26

nocturn In the Roman Catholic Church, one of the three divisions of the service of matins, previously held at midnight but now usually at daybreak.
Found on
http://www.wordinfo.info/words/index/info/view_unit/1402/2

the office of matins, consisting of nine psalms and either three or nine lessons.
Found on
https://www.infoplease.com/dictionary/nocturn
No exact match found.