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