Emily Dickinson Lexicon

TRI-EN'NI-AL, a. [Fr. triennal; L. triennis, triennium; tres, three, and annus, year.]

1. Continuing three years; as, triennial parliaments.
2. Happening every three years; as, triennial elections. Triennial elections and parliaments were established in England in 1695; but these were discontinued in 1717, and septennial elections and parliaments were adopted, which still continue.