From Longman Dictionary of Contemporary Englishbiannualbi‧an‧nu‧al /baɪˈænjuəl/ adjective TMCTWOhappening twice each year a biannual report → annual, biennial
Examples from the Corpus
biannual• It is for the benefit of the inspectors who come up from Paris for the biannual audits.• An independent data and safety monitoring board compared the frequency of all adverse events in the two groups during three biannual meetings.• In late spring, Jody flies to San Francisco for the biannual Pac-10 coaches meeting.From Longman Business Dictionarybiannualbi‧an‧nu‧al /baɪˈænjuəl/ adjective happening twice each yearWildlife Link’s biannual liaison meeting with the Forestry Committee → compare biennial 