1) Biennial 2) Biyearly 3) Coming twice a year 4) Every other quarter 5) Happening every two years 6) Like equinoxes 7) Like House elections 8) Like some dental checkups 9) Like some performance reviews 10) Like the Olympics, nowadays 11) Occuring twice a year 12) Occurring every two years 13) Occurring twice a year 1) Semiannual 
• (a.) Occurring twice a year; half-yearly; semiannual.
Bi·an'nu·al adjective [ Prefix bi- + annual .] Occurring twice a year; half-yearly; semiannual. 
A frequency of every six months; twice a year
biannual A biannual event occurs twice a year; a biennial event takes place once in two years.
occurring twice a year; semiannual. · occurring every two years; biennial.
occurring or payable twice each year