[adj] - occurring every two weeks 2. [adv] - every two weeks
Fort'night`ly adjective Occurring or appearing once in a fortnight; as, a fortnightly meeting of a club; a fortnightly magazine, or other publication. -- adverb Once in a fortnight; at intervals of a fortnight. 
biweekly adjective occurring every two weeks
biweekly adverb every two weeks; `he visited his cousins fortnightly`
• (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.