barrier reef

barrier reef A coral reef, stretching along a line parallel with the coastline but separated from it by a wide, deep lagoon, the most famous of which is the Great Barrier Reef off north‐west Australia. Also classified as barrier reefs are those coral reefs encircling islands, one of the best examples being the Turk group in the Caroline Islands. The coral on a barrier reef builds up to the level of low tides. See also coral reef.