triweekly

1. not comparableOccurring three times per week.
2. not comparableOccurring once every three weeks.
3. not comparablePublished three times a week.

   This string of daily papers in Aurora, Joliet, Elgin, and Waukegan, the triweekly Naperville Sun, and 13 Sun suburban weeklies, has been winning major press-photography awards hand over fist in recent years.

   2001 June 29, Michael Miner, “We Are Teachers, Hear Us Roar/Remembering Those Who Dodged”, in Chicago Reader

   1 more example

   And then it appeared to be forgotten, or, at least, men seldom spoke of it, and presently it came to be accepted as the popular belief that the robbery had been committed by a gang of desperate tramps, this theory being confirmed by a certain exploit subsequently in the San Juan country, an exploit wherein three desperate tramps assaulted the triweekly road-hack, and, making off with their booty, were ultimately taken and strung up to a convenient tree.

   1911, Eugene Field, Second Book of Tales

plural triweeklies

1. A publication published three times a week.