American Dictionary of the English Language

BIEN'NIAL, adjective [Latin biennis, of bis, twice, and annus, a year.]

1. Continuing for two years and then perishing; as plants, whose root and leaves are formed the first year, and which produce fruit the second.

2. In botany, continuing for two years and then perishing; as plants, whose root and leaves are formed the first year, and which produce fruit the second.