Semiyearly Definition

sĕmē-yîrlē, sĕmī-
semiyearly
adjective
Done, happening, appearing, etc. every half year or twice a year.
Webster's New World
noun
A semiyearly event or publication.
American Heritage
adverb
Every half year.
American Heritage
Twice yearly.
Webster's New World

(uncommon) Semiannually.

Wiktionary