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Webster 1913 Edition

Noun.

[NL., from Gr. [GREEK] to fall in before; [GREEK] before + [GREEK] in + [GREEK] to fall.]

(Chron.)

The addition of a day to the lunar calendar.

[R.]

See

Noun.

[Gr. to fall before.] In chronology, the lunar equation or addition of a day, necessary to prevent the new moon from happening a day too soon.

proemptosis ‎(plural not attested)