ATOLL
atoll
(noun) an island consisting of a circular coral reef surrounding a lagoon
Source: WordNet® 3.1
Etymology
Noun
atoll (plural atolls)
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
Anagrams
• all to, allot
Source: Wiktionary
A*toll", n. Etym: [The native name in the Indian Ocean.]
Definition: A coral island or islands, consisting of a belt of coral reef,
partly submerged, surrounding a central lagoon or depression; a
lagoon island.
Source: Webster’s Unabridged Dictionary 1913 Edition