Croatia UK /ˌkɹəʊˈeɪ.ʃə/US /ˌkɹoʊˈeɪ.ʃə/ noun1 •A country on the Balkan Peninsula in Southeastern Europe. Official name: Republic of Croatia. Capital and largest city: Zagreb. Part of Yugoslavia until 1991.The violence began when Serbian troops went into Croatia ostensibly to aid armed ethnic Serbians trying to create their own autonomous states there. — 2015