AROO, or ARRU, a group of islands in the Eastern Archipelago, lying about 80 miles south-west of Papua, between Lat. 5. 20. and 6. 55. S.; and Long 134. 10. and 134. 45. E. These islands produce pearl, mother-of-pearl, tortoise-shell, birds of paradise, edible birds'-nests, trepang, &c. The inhabitants are a mixture of the Malay and Australasian negro races. The largest of these islands is 70 miles long and 20 broad.