Tri*en"ni*al (?), a. [L. triennium the space of three years; tri- (see Tri-) + annus year. See Annual.]
1.
Continuing three years; as, triennial parliaments; a triennial reign.
Howell.
2.
Happening, coming about, or appearing once in every three years; as, triennial elections; a triennial catalogue; a triennial visitation.
T. Warton.
© Webster 1913.
Tri*en"ni*al, n.
Something which takes place or appears once in three years.
© Webster 1913.