TMCa year, which happens every fourth year, when February has 29 days instead of 28 闰年
Examples from the Corpus
leap year• This is a leap year, so use that extra day to plan some great outings.• Knock! jokes are okay in small doses - like one every second leap year.• The leap year proposal ceremony was conducted near the player's entrance by Ayresome Park disc jockey Mark Page.
Originleap year
(1300-1400) Perhaps because a date in such a year "jumps" one day ahead of the day on which it would otherwise have fallen