In·do·ne·si·a /ˌɪndəʊˈniːziə, -ˈniːʒə $ -ˈniːʒə, -ˈniːʃə/ a country in the southeast Indian Ocean consisting of more than 13,000 islands, the largest of which are Java, Sumatra, most of Borneo, Sulawesi, and Bali. Population: 251,160,124 (2014). Capital: Jakarta. In population, it is the fourth largest country in the world, and its official religion is Islam. —Indonesian noun, adjectiveadj