bĭennis, e, adj. [biennium],
of two years , lasting two years (very rare): biennis quasi duorum annorum, Beda, p. 2331 P.; Macr. S. 6, 9, 6; Serv. ad Verg. A. 4, 57; Nigid. ap. Gell. 16, 6, 13 (but in the phrase bienni spatio, Suet. Galb. 15; Plin. 2, 82, 84, § 198 Jan., bienni is the gen. of biennium).