meˈtänik- noun
Usage: usually capitalized M
Etymology: Meton, 5th century B.C. Greek astronomer + English -ic
: a period of 19 years after the lapse of which the phases of the moon return to a particular date in the calendar year:
a. : one of the 19-year periods reckoning from June 27, 432 B.C., that were used in determining lengths of years and the placing of the intercalary month in the ancient Greek calendar
b. : one of the 19-year periods reckoning from 1 B.C. that are used in determining the date of Easter in the Gregorian calendar