e·chi·no·derm  (ĭ-kī'nə-dûrm')  n. 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. [From New Latin Echinodermata, phylum name : echino- + -dermata, -skinned (from Greek derma, dermat-, skin; see -derm).] e·chi'no·der'mal, e·chi'no·der'ma·tous (-dûr'mə-təs) adj. |