The Collaborative International Dictionary of English v.0.48:

Belgrade \Belgrade\ prop. n. (Geography)
   The capital city of Yugoslavia. Population (2000) =
   1,168,454.
   [PJC]

WordNet (r) 3.0 (2006):

Belgrade
    n 1: capital and largest city of Serbia and Montenegro; situated
         on the Danube [syn: Belgrade, Beograd, capital of
         Serbia and Montenegro]