Source : Webster's Revised Unabridged Dictionary (1913)

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 : WordNet®

semiweekly
     adj : occurring twice a week [syn: {biweekly}]
     adv : twice a week; "he called home semiweekly" [syn: {biweekly}]