1. Occurring or payable twice each year
   "You must submit biyearly compliance reports";
   - semiannual, biannual, half-yearly
    
2. Occurring every second year
   "they met at biyearly conventions";
   - biennial

1. Twice a year
   "The company releases financial reports biyearly";
   - semiannually
    
2. Every two years
   "this festival takes places biyearly";
   - biennially

See also: periodic, periodical