I. (ˈ)bī|enēəl, -nyəl adjective
Etymology: Latin bienni um period of two years (from bi- + -ennium, from annus year) + English -al — more at annual
1. : occurring, appearing, or being made, done, or acted upon every two years — compare biannual
2. : continuing or lasting for two years — used specifically of plants (as the parsnip) that require two growing seasons in which to go from seed to seed; compare annual
II. noun
( -s )
: something that is biennial (as an exhibition or examination) ; especially : a biennial plant