brain coral

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several reef-building corals of various genera, especially Diploria, that form rounded colonies resembling the convolutions of the human brain.

from The Century Dictionary.

• noun The popular name of coral of the genus Meandrina: so called because it resembles in its superficial appearance the convolutions of the human brain.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of several species of coral in the shape of a brain.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun massive reef-building coral having a convoluted and furrowed surface