Merriam-Webster Logo
SINCE 1828
Menu
dictionary thesaurus

keyhole urchin

noun

Definition of keyhole urchin

: a flat sea urchin of the order Exocycloida with long narrow apertures occurring near the margin of the test

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

  • More than 250,000 words that aren't in our free dictionary
  • Expanded definitions, etymologies, and usage notes
  • Advanced search features
  • Ad free!

Learn More about keyhole urchin

Statistics for keyhole urchin

Look-up Popularity

Comments on keyhole urchin

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

Show Comments  Hide Comments 

WORD OF THE DAY

propitious

Listen to the pronounciation of propitious

likely to have or produce good results

Get Word of the Day daily email!

Test Your Vocabulary

Words from Greek and Latin Quiz

  • roman forum
  • Which of the following months comes from a Latin word for “ten”?
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
Ask the Editors
Word Games