Islamic nation; Muslim country
Refers to a country where Islam is the dominant religion or the state religion. Note that 回教 is an older term for Islam; イスラム教 is more common today.
インドネシアは世界最大の回教国です。
Indonesia is the world's largest Islamic nation.
Compound of 回教 (かいきょう, 'Islam', literally 'Hui religion', an older term) and 国 (こく, 'country').