n. Originally, the interval from one new moon to the next, called specifically a lunar, synodical, or illuminative month.n. One twelfth part of a tropical year, or 30 days, 10 hours, 29 minutes, 3. 8 seconds: called specifically a solar month.n. One of the twelve parts into which the calendar year is arbitrarily divided: called specifically a calendar month.n. At common law and in equity, month has been understood to mean ‘a lunar month,’ which is assumed to be 28 days, except when the contrary appears, and except when used of mercantile transactions, such as negotiable paper, etc.n. plural Same as menses. Minsheu; Cotgrave. Abbreviated mo.