'Tercentenary' definitions:

Definition of 'tercentenary'

From: WordNet
noun
The 300th anniversary (or the celebration of it) [syn: tercentennial, tercentenary, triennial]

Definition of 'Tercentenary'

From: GCIDE
  • Tercentenary \Ter*cen"te*na*ry\, a. [L. ter thirce + E. centenary.] Including, or relating to, an interval of three hundred years. -- n. The three hundredth anniversary of any event; also, a celebration of such an anniversary. [1913 Webster]