Marshall Islands UK /ˈmɑː.ʃəl ˈaɪ.ləndz/US /ˈmɑɹ.ʃəl ˈaɪ.ləndz/ noun1 •A country consisting of two archipelagos in Micronesia, in Oceania. Official name: Republic of the Marshall Islands. Capital and largest city: Majuro.