2.a porous mass of interlacing fibers the forms the internalskeleton of various marine animals and usable to absorb water or any porous rubber or cellulose product similarly used.
4.Any of numerous radially symmetrical marine invertebrates of the phylum Echinodermata, which includes the starfishes, sea urchins, and sea cucumbers, having an internal calcareous skeleton and often covered with spines.