Simple Definition of sea urchin

from our Learner's Dictionary

sea urchin

noun

plural sea urchins
: a small sea animal that lives on the ocean floor and is covered in sharp spines

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“Sea urchin.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/sea%20urchin. Accessed 20 Jun. 2026.

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