sea fan

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

• noun Any of various gorgonian corals having a flexible branching skeleton in the shape of a fan.

from The Century Dictionary.

• noun An alcyonarian polyp of the suborder Gorgoniacea, and especially of the family Gorgoniidæ, as Rhipidogorgia flabellum. See cuts under Alcyonaria, coral, and Rhipidogorgia.

from the GNU version of the Collaborative International Dictionary of English.

• (Zoöl.) Any gorgonian which branches in a fanlike form, especially Gorgonia flabellum of Florida and the West Indies.

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

• noun Any gorgonian which branches in a fan-like form, especially Gorgonia flabellum of Florida and the West Indies.

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

• noun corals having a treelike or fan-shaped horny skeleton