The term PART OF AN ATOLL can be solved by the crossword solution ISLAND, which is a 6 letter word. An atoll is a ring-shaped coral reef, island, or chain of islands formed of coral. It typically encircles a lagoon partially or completely. The islands that make up an atoll are usually low-lying and are composed of sand and coral debris. The part of an atoll referred to as an island is the land mass that is surrounded by the lagoon.