1. intercalary month (lunar calendar); leap month
Wikipedia definition
2. IntercalationIntercalation is the insertion of a leap day, week or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.
Read “Intercalation” on English Wikipedia
Read “閏月” on Japanese Wikipedia
Read “Intercalation” on DBpedia
Other forms
うるう月 【うるうづき】閏月 【じゅんげつ】


to talk about this word.