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 (bī-sĕk′stĭl, -stīl′, bĭ-)
1. Of or relating to a leap year.
2. Of or relating to the extra day falling in a leap year.
A leap year.

[Late Latin bissextīlis, containing an intercalary day, from bisextus (diēs), bis sextus (diēs) and Latin bisextum, intercalary day : bis, twice; see bis + sextus, sixth (because the sixth day before the Calends of March on February 24 occurred twice every leap year); see sext1.]


(Units) (of a month or year) containing the extra day of a leap year
a rare name for leap year
[C16: from Late Latin bissextilis annus leap year, from Latin bissextus, from bi-1 + sextus sixth; referring to February 24, the 6th day before the Calends of March]
References in periodicals archive ?
This corresponds to 8 years minus 2 days (or 8 years minus 1 day if the interval includes a non bissextile century year), and approximates within two days to 13 sidereal revolutions of the planet.
59 pm on 31 December 1999, or even by following Joyce's conversion in Ulysses of 'the bissextile year one thousand nine hundred and four of the Christian era' into the 'jewish era five thousand six hundred and sixtyfive, mohammedan era one thousand three hundred and twentytwo' (p.