Emily Dickinson Lexicon

ME-TEMP-TO'SIS, n. [Gr. μετα, after, and πιπτω, to fall.]

In chronology, the solar equation necessary to prevent the new moon from happening a day too late, or the suppression of the bissextile once in 134 years. The opposite to this is the proemptosis, or the addition of a day every 300 years, and another every 2400 years. Encyc.