leap year

American  

noun

1. (in the Gregorian calendar) a year that contains 366 days, with February 29 as an additional day: occurring in years whose last two digits are evenly divisible by four, except for centenary years not divisible by 400.

2. a year containing an extra day or extra month in any calendar.

---

leap year British  

noun

1. a calendar year of 366 days, February 29 ( leap day ) being the additional day, that occurs every four years (those whose number is divisible by four) except for century years whose number is not divisible by 400. It offsets the difference between the length of the solar year (365.2422 days) and the calendar year of 365 days

---

Etymology

Origin of leap year

1350–1400; Middle English lepe yere

Example Sentences

At this point we observe a leap year, an extra day in the calendar, allowing the solstice to revert back to its earlier date.

From BBC

The calendar is approximately a quarter of a day short, which is why we have leap years, to bring the calendar back in line with the Earth's orbit.

From BBC

Like clockwork, leap years roll around every four years.

From New York Times

What is a leap years and why do we have them?

From BBC

The extra accrued time results in Feb. 29 appearing on the calendar every fourth year — leap year — to help the seasons line up.

From Los Angeles Times