noun ·Rare ·Advanced level

Definitions

Noun

1. 1
   A colony of coral, usually 1-3 metres in diameter that is dead on the top as a result of exposure at low tide.

Etymology

From micro- + atoll, because the colonies superficially resemble atolls, but are much smaller.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.