Biweekly

bihebdomadaire

(occurring twice a week)

bimensuel

(occurring every two weeks)

bihebdomadairement

(twice a week)

deux fois par semaine

(twice a week)

quinzomadairement

(every two weeks)

tous les quinze jours

(every two weeks)

toutes les deux semaines

(every two weeks)

bimensuel

(something published or released once every two weeks)

quinzomadaire

(something published or released once every two weeks)