atoll
noun
- ring-shaped coral reef, generally formed over a former oceanic volcan, frequently with small emerging islands (motus) over the rim, often enclosing a central lagoon possibly still containing one or a few emerging elevated islands
Wiktionary
Pronunciation: /ˈætɒl/ / /əˈtɒl/ / /ˈætɔl/
noun
Etymology: Borrowed from Portuguese atol, from Dhivehi އަތޮޅު (atoḷu), possibly from Prakrit *𑀲𑀁𑀢𑀻𑀞 (*saṃtīṭha), from Sanskrit *संतीर्थ (*saṃtīrtha, “level ford”). The traditional etymology from Persian آبتل (âb-tal, “water-hillock”) is unlikely.
- A type of island consisting of a ribbon reef that nearly or entirely surrounds a lagoon and supports, in most cases, one to many islets on the reef platform.