brittle star

The term refers specifically to ophiuroids, which are distinct from common sea stars (asteroids). The name derives from the animal's ability to autotomize, or intentionally shed, its arms to escape predators, a biological defense mechanism that makes the limbs appear fragile or brittle.

In a scientific context, the term is used neutrally to describe a specific taxonomic group. Because it is a compound noun describing a biological species, it follows standard English pluralization rules for animals.