Tri"week`ly (?), a. [Pref. tri- + weekly.] Occurring or appearing three
times a week; thriceweekly; as, a triweekly newspaper. — adv. Three
times a week. — n. A triweekly publication.
This is a convenient word, but is not legitimately formed. It should
mean occurring once in three weeks, as triennial means once in three
years. Cf. Biweekly.