sexcentenary

adjective

1. pertaining to 600 or a period of 600 years; marking the completion of 600 years.

noun, plural sex·cen·ten·ar·ies.

2. a 600th anniversary or its celebration.

adjective

1. of or relating to 600 or a period of 600 years
2. of, relating to, or celebrating a 600th anniversary

noun plural -naries

3. a 600th anniversary or its celebration