atoll

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.

noun

1. 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. Atolls have a unique geology, so not all islands with a reef and a lagoon are atolls.