From Longman Dictionary of Contemporary Englishbiennialbi‧en‧ni‧al /baɪˈeniəl/ adjective 1 TMCTWOa biennial event happens once every two years → annual2 HBPa biennial plant stays alive for two years → annual, perennial —biennially adverb
Examples from the Corpus
biennial• The Six eventually reached a compromise in November 1959, agreeing that the foreign ministers should meet regularly on a biennial basis.• However, the biennial consideration of High Court Interlocutory fees produced an uprating of just under ten percent over two years.• The biennial exercise involves more than 12,000 Marines, sailors and airmen, 24 ships and dozens of aircraft.• Some legislators set up housekeeping when the biennial gatherings began and played house for the six-month sessions.• Since 1982 biennial national surveys conducted by the Office of Population Censuses and Surveys have provided valuable information on adolescent smoking behaviour.• The money does not go to Brown, whose re- election in a safe Democratic district has been a biennial slam-dunk.• The unit was one of dozens participating in the Kernel Blitz 97 biennial war game at Camp Pendleton.From Longman Business Dictionarybiennialbi‧en‧ni‧al /baɪˈeniəl/ adjective happening once every two yearsthe biennial report published by the BDDA → compare biannualOrigin biennial (1600-1700) Latin biennium “two-year period”, from bi- ( → BI-) + annus “year” 