| Atoll (n.) A coral island or islands, consisting of a belt of coral reef, partly submerged, surrounding a central lagoon or depression; a lagoon island. Thesaurus Entries ait, archipelago, bar, cay, continental island, coral head, coral island, coral reef, holm, insularity, island, island group, islandology, isle, islet, key, oceanic island, reef, sandbank, sandbar |