Толковый словарь английского языка Oxford English Reference - biennial

adj. & n. --adj. 1 lasting two years. 2 recurring every two years (cf. BIANNUAL). --n. 1 Bot. a plant that takes two years to grow from seed to fruition and die (cf. ANNUAL, PERENNIAL). 2 an event celebrated or taking place every two years. Derivatives biennially adv. Etymology: L biennis (as BI-, annus year)