Using bi or semi in front of time periods can create confusion for some.
Biweekly: once every two weeks or twice a week
Bimonthly: once every two months or twice a month
In addition, a biweekly publication is issued every two weeks and a bimonthly publication is issued every two months.
Then we have this from The Associated Press Stylebook:
Biannual: twice a year, synonymous with semiannual; for “every two years,” use biennial.
Consider these definitions as well:
Semiweekly: twice a week
Semimonthly: twice a month
Instead of trying to figure out if we should say biweekly or semiweekly, we just say “every two weeks.” Rather than wrestle with bimonthly or semimonthly, we will write or say “twice a month.”