Semicentennial

[semisen'tenjәl]

(noun.) the 50th anniversary (or the celebration of it).

(adj.) of or relating to or marking the 50th anniversary .

Editor: Luke--From WordNet

(a.) Of or pertaining to half of a century, or a period of fifty years; as, a semicentennial commemoration.

(n.) A fiftieth anniversary.

Checked by Joseph