Having an intercalary day, particularly the quadrennial leap day of the Julian and Gregorian calendars traditionally placed as a "second sixth" day before March 1st.
A year in the Julian or Gregorian calendars with an intercalary day added to February, used to adjust for the extra hours of the solar year; a 366-day year.
(inexact) Any other year featuring intercalation, such as a year in a lunisolar calendar with 13 months instead of 12, used to maintain its alignment with the seasons of the solar year.
