Biennial

happening every two years:
biennial games.
lasting or enduring for two years:
a biennial life cycle.
Botany. completing its normal term of life in two years, flowering and fruiting the second year, as beets or winter wheat.
any event occurring once in two years.
Botany. a biennial plant.
Contemporary Examples

Whitney Museum’s Biennial: A Big Yawn Blake Gopnik February 29, 2012
The Biennial’s Breakout Star Rachel Wolff February 24, 2010
Who Else Opposes An Iran Attack? Ali Gharib September 10, 2012

Historical Examples

Elements of Civil Government Alexander L. Peterman
Grasses H. Marshall Ward
The University of Michigan Wilfred Shaw
The Manual of the Botany of the Northern United States Asa Gray
The Field and Garden Vegetables of America Fearing Burr
Island Life Alfred Russel Wallace
A Garden with House Attached Sarah Warner Brooks

adjective
occurring every two years
lasting two years Compare biannual
noun
a plant, such as the carrot, that completes its life cycle within two years, developing vegetative storage parts during the first year and flowering and fruiting in its second year Compare annual (sense 3), perennial (sense 3)
an event that takes place every two years
adj.
biennial
(bī-ěn’ē-əl)
Adjective Completing a life cycle normally in two growing seasons.

Noun A biennial plant. In the first year, biennials normally produce a short stem, a rosette of leaves, and a fleshy root that acts as food supply. In the second season, biennials blossom, produce seed, use up their food supply, and die. Carrots, parsnips, and sugar beets are examples of biennials. Compare annual, perennial.