echinoid

adjective

1. belonging or pertaining to the class Echinoidea, comprising mainly sea urchins and sand dollars.

noun

2. any echinoderm of the Echinoidea.

noun

1. any of the echinoderms constituting the class Echinoidea, typically having a rigid ovoid body. The class includes the sea urchins and sand dollars

adjective

2. of or belonging to this class