quinquagenary
/kwɪŋˈkwadʒɪn(ə)ri/ /kwɪnˈkwadʒɪn(ə)ri/rare
noun
A fiftieth anniversary; the celebration of such an anniversary.
adjective
Of or relating to a fiftieth anniversary.
Origin
Late Middle English (in an earlier sense). From classical Latin quīnquāgēnārius.