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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 ?
rent au calend une annAaAaAeA@e bissextile tous les 3 ans.
Mais la frequence de ce [beaucoup moins que] sixieme jour bis [beaucoup plus grand que] n'etait pas suffisante pour combler une difference de revolution : ce calendrier ne distinguait pas les fins de siecle, et donc imposait une annee bissextile tous les quatre ans, sans exception, point barre.
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.