Merriam-Webster Logo
SINCE 1828
Menu
×

An Encyclopædia Britannica Company

sea urchin

noun

Definition of sea urchin

  1. :  any of numerous echinoderms (class Echinoidea) that are usually enclosed in thin brittle globular tests covered with movable spines

See sea urchin defined for English-language learners

See sea urchin defined for kids

Explore M-W

alt-594d2b6325245
'Pride': The Word That Went From Vice to Strength
alt-594ab41a604d2
Trending: Kim and Kanye Might Have Hired a Surrogate Mother
istock-refers-to-this-as-a-tumble-of-strawberries-which-sounded-pretty-nice-to-us
June 2017 Words of the Day Quiz
image599301899
Pretty in 'Pink'

1591

First Known Use of sea urchin

1591

SEA URCHIN Defined for English Language Learners

sea urchin

noun

Definition of sea urchin for English Language Learners

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

SEA URCHIN Defined for Kids

sea urchin

noun

Definition of sea urchin for Students

  1. :  a small sea animal that is related to the starfish, lives on the sea bottom, and is enclosed in a roundish shell covered with spines that can move

Learn More about sea urchin

  1. Spanish Central: Translation of sea urchin Nglish: Translation of sea urchin for Spanish speakers Britannica.com: Encyclopedia article about sea urchin

Seen and Heard

What made you want to look up sea urchin? Please tell us where you read or heard it (including the quote, if possible).

show hide

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

perspicuous

play

clear to the understanding

Get Word of the Day daily email!

TRENDING NOW

  1. surrogate mother From TMZ to the dictionary.

  2. zealot A fanatical partisan

  3. stonewall to be uncooperative, obstructive, or evasive

  4. scurrilous Containing obscenities, abuse, or slander

  5. depose That word might not mean what you think it means.

SEE ALL

BROWSE DICTIONARY

sea urchin

WORD GAMES

Take a 3-minute break and test your skills!

  • istock-refers-to-this-as-a-tumble-of-strawberries-which-sounded-pretty-nice-to-us
  • Which is a synonym of garner?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Words at Play

alt-594d2b6325245
'Pride': The Word That Went From Vice to Strength

Do you take pride in Pride?

image599301899
Pink: The Color that Will Change Your Life

From Fuchsia to Baker-Miller Pink

image2144101468
That Sucks Word Alternatives

Your day is the worst. Your vocabulary is the best.

alt-5931949575ca5
'All the Feels,' All the Time

Once more, with 'feels'

Ask the Editors

decimate-video
Is it wrong to use 'decimate' to mean 'destroy'?

Language changes

serial-comma
The Serial Comma

Why don't they call it the Merriam-Webster comma?

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless
Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals
Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

istock-refers-to-this-as-a-tumble-of-strawberries-which-sounded-pretty-nice-to-us
June 2017 Words of the Day Quiz

Summer's first WOTD quiz.

Take the quiz
alt-5941ad7527c3c
Yearbook Superlatives Quiz

Is that your picture under "Largest Vocabulary"?

Take the quiz
Name That Thing
Name That Thing

Test your visual vocabulary with our 10-question challenge!

Take the quiz
Word Winder's CrossWinder
Word Winder's CrossWinder

A game of winding words.

Play the game