trienal

Adjective

 * 1) triennial (lasting three years)
 * 2) triennial (occurring every three years)

Adjective

 * 1) triennial happening every three years

Noun

 * 1) an event that is held every three years

Etymology
.

Adjective

 * 1) triennial

Adjective

 * 1) three-year, triennial