(1)1週間か2週間（104冊か1年あたり26冊）に二度発行される定期刊行物
(2)a periodical that is published twice a week or every two weeks (either 104 or 26 issues per year)
さらに詳しく
(1)週に2回
(2)隔週に
(3)twice a week
(4)every two weeks; "he visited his cousins fortnightly"
