1Roman Catholic Church
The commemoration of a deceased person by the celebration of a requiem mass, prayers, etc., on a day one month from the date of the death or funeral.
The term is still common among Irish and Scottish Catholics, though not used in England since the Reformation. There seems to be no authority for applying the term to a commemoration lasting throughout the month following the funeral, and likewise for the notion of a commemoration celebrated recurrently every month. For an English rustic survival of the ‘month's mind’ custom, see "month's end".
2dialect Used allusively or humorously as a synonym for "mind": an inclination, fancy, liking. Especially in "to have (also bear) a month's mind". "to be in a month's mind": to have a strong expectation (rare).
Late Middle English. From the genitive of month + mind. Compare post-classical Latin dies mensis, dies mensis obitus.