biannual
adj.
also bi-annual; "occurring every six months, twice a year," 1837, from bi- + annual. Related: Biannually; bi-annually.
〔李〕[bi-=twice 两次的；annual a.一年的→] a. twice in a year 每年两次的
〔李〕[bi-=two, twice二，两次；annu=year年；-al a.=of……的→a. of twice a year每年两度的