Proemptosis

• (n.) The addition of a day to the lunar calendar.
Found on http://thinkexist.com/dictionary/meaning/proemptosis/

Proemptosis

Pro`emp·to'sis noun [ New Latin , from Greek ... to fall in before; ... before + ... in + ... to fall.] (Chron.) The addition of a day to the lunar calendar. [ R.] See Metemptosis .
Found on http://www.encyclo.co.uk/webster/P/168

proemptosis

addition of extra day to lunar calendar every 300 years
Found on http://phrontistery.info/p.html
No exact match found