semicentennial Meaning, Definition & Usage

  1. noun the 50th anniversary (or the celebration of it)
    semicentenary.
  2. adjective of or relating to or marking the 50th anniversary
    semicentenary.

WordNet

Sem`i*cen*ten"ni*al adjective
Definitions
  1. Of or pertaining to half of a century, or a period of fifty years; as, a semicentennial commemoration.
Sem`i*cen*ten"ni*al noun
Definitions
  1. A fiftieth anniversary.

Webster 1913