noun
intercalary month; leap month
A month inserted into a lunar calendar to keep it aligned with the solar year. Used in traditional East Asian calendars.
旧暦では、約三年に一度、閏月が挿入される。
In the old lunar calendar, an intercalary month is inserted about once every three years.
今年は閏月があるので、季節と月のずれが調整さ
This year has a leap month, so the seasonal drift is adjusted.
閏年 refers to a leap year in the Gregorian calendar, while 閏月 is a leap month in a lunar calendar.
閏 (intercalary) + 月 (month). The reading うるうづき is a native Japanese reading (kun'yomi) of the kanji compound, while じゅんげつ is the Sino-Japanese reading (on'yomi).