\(\def\|{&}\)
The description of the word you requested from the astronomical dictionary is given below.
[Greek] embolos = something put in between
Embolistic means "put in between". An embolistic month is an extra month that is added to the calendar only in certain years, usually to keep a lunar calendar in line with the tropical year. The embolistic day of the Julian and Gregorian calendars is more commonly called the bissextile day.