The Collaborative International Dictionary of English v.0.48:

Western \West"ern\, a.
   [1913 Webster]
   1. Of or pertaining to the west; situated in the west, or in
      the region nearly in the direction of west; being in that
      quarter where the sun sets; as, the western shore of
      France; the western ocean.
      [1913 Webster]

            Far o'er the glowing western main.    --Keble.
      [1913 Webster]

   2. Moving toward the west; as, a ship makes a western course;
      coming from the west; as, a western breeze.
      [1913 Webster]

   Western Church. See Latin Church, under Latin.

   Western empire (Hist.), the western portion of the Roman
      empire, as divided, by the will of Theodosius the Great,
      between his sons Honorius and Arcadius, a. d. 395.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Western Empire
    n 1: the western part after the Roman Empire was divided in 395;
         it lasted only until 476 [syn: Western Roman Empire,
         Western Empire]