triennial Meaning, Definition & Usage

  1. noun the 300th anniversary (or the celebration of it)
    tercentennial; tercentenary.
  2. adjective satellite occurring every third year or lasting 3 years

WordNet

Tri*en"ni*al adjective
Etymology
L. triennium the space of three years; tri- (see Tri-) + annus year. See Annual.
Definitions
  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.
Tri*en"ni*al noun
Definitions
  1. Something which takes place or appears once in three years.

Webster 1913