Of or relating to a span of 300 years or to a 300th anniversary. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "tercentenary" in a sentence
"(Dave Lull reminds me that the good doctor's tercentenary is only three years away."
"Prize – the Prize in Economic Sciences in Memory of Alfred Nobel, donated by the Bank of Sweden to celebrate its tercentenary in 1968."
"In conjunction with its tercentenary celebrations in 1968, Sveriges Riksbank (the central bank of Sweden) instituted a new award, "The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel" on the basis of an economic commitment by the bank in perpetuity."