E'pāct, n.

n. [Fr. épacte, from Gr. ἐπακτός, brought on or in, added, from ἐπάγειν, to bring on or in, to adduce, from ἐπὶ and ἄγειν, to bring or lead to. See supra.] (Chron.) The moon's age at the end of the year, or the number of days by which the last new moon has preceded the beginning of the year.

Menstrual or monthly epact, the excess of a calendar month over a lunar. — Annual epact, the excess of a solar over a lunar year, being eleven days.