quin·cen·ten·a·ry (kwĭn'sěn-těn'ə-rē, kwĭn-sěn'tə-něr'ē) n.
pl.quin·cen·ten·a·ries A 500th anniversary or celebration. adj. Of or relating to a span of 500 years or to a 500th anniversary.
[From Latin quīngentī, quīncentī, five hundred (on the model of such words as tercentenary); see penkwe in Indo-European roots.]