'Sea urchin' definitions:
Definition of 'sea urchin'
(from WordNet)
noun
Shallow-water echinoderms having soft bodies enclosed in thin spiny globular shells
Definition of 'Sea urchin'
From: GCIDE
- Sea urchin \Sea" ur"chin\ (Zool.) Any one of numerous species of echinoderms of the order Echinoidea.
- Note: When living they are covered with movable spines which are often long and sharp. [1913 Webster]