I. (ˈ)trī+ adjective
Etymology: tri- + weekly
1. : occurring, appearing, or being made, done, or acted upon three times a week
a triweekly publication
triweekly train service
2. : occurring, appearing, or being made, done, or acted upon every three weeks
II. noun
: a triweekly publication
III. adverb
: three times a week
a newspaper published triweekly