n. [ Contr. fr. fourteen nights, our ancestors reckoning time by nights and winters; so, also, seven nights, sennight, a week. ] The space of fourteen days; two weeks. [ 1913 Webster ]
a. Occurring or appearing once in a fortnight; as, a fortnightly meeting of a club; a fortnightly magazine, or other publication. -- adv. Once in a fortnight; at intervals of a fortnight. [ 1913 Webster ]