Occurring twice a year; semiannual.
Occurring once every two years; biennial.
Something occurring twice each year.
Happening every two years.
Lasting for two years.
A germinating and growing in its first year, then producing its flowers and fruit in its second year, after which it usually dies.
taking place every other year
“the first of a series of biennial exhibitions”
(of a plant) taking two years to grow from seed to fruition and die.
a biennial plant.
an event celebrated or taking place every two years
“the top antiques fairs are the Milan and Florence biennials”