bikini atoll
a group of small coral islands in the shape of a ring that encloses a lagoon
the oppsite of atoll is planet
An atoll is formed first as a reef that fringes a volcanic island. As the island sinks (after the volcanic activity has ceased and the crust has cooled, becoming denser), the reef continues to build upward, eventually ending up as a ring-shaped structure.
Atoll is a noun.
bikini atoll
Allot and atoll.
A atoll
Let's not strand ourselves on this atoll.
The population of Rongelap Atoll is 19.
Utirik Atoll's population is 409.
Wotho Atoll's population is 160.
The population of Namu Atoll is 801.