Semiweekly \Sem`i*week"ly\, a. Coming, or made, or done, once every half week; as, a semiweekly newspaper; a semiweekly trip. -- n. That which comes or happens once every half week, esp. a semiweekly periodical. -- adv. At intervals of half a week each.

Source: Webster's Revised Unabridged Dictionary (1913)