Triennial

[traɪ'enɪəl] or [traɪ'ɛnɪəl]

(adj.) occurring every third year or lasting 3 years .

Edited by Denny--From WordNet

(a.) Continuing three years; as, triennial parliaments; a triennial reign.

(a.) Happening, coming about, or appearing once in every three years; as, triennial elections; a triennial catalogue; a triennial visitation.

(n.) Something which takes place or appears once in three years.

Typed by Lillian

adj. continuing three years: happening every third year.—adv. Trienn′ially.

Typed by Hannah