A circular growth of coral a few metres in diameter and with a central depression, such as is found in intertidal areas in warm seas and on the flats inside a coral reef.
Origin
1930s.
Definition of microatoll in US English:
microatoll
noun
A circular growth of coral a few metres in diameter and with a central depression, such as is found in intertidal areas in warm seas and on the flats inside a coral reef.