protostome

noun
pro·​to·​stome | \ ˈprō-tə-ˌstōm How to pronounce protostome (audio) \

Definition of protostome

: any of a major group (Protostomia) of bilateral metazoan animals (such as mollusks, annelids, and arthropods) characterized in typical forms by determinate and spiral cleavage, formation of a mouth and anus directly from the blastopore, and formation of the coelom by splitting of the embryonic mesoderm — compare deuterostome

First Known Use of protostome

1959, in the meaning defined above

History and Etymology for protostome

New Latin Protostomia, from prot- + Greek stoma mouth — more at stomach

Keep scrolling for more

Learn More about protostome

Statistics for protostome

Look-up Popularity

Time Traveler for protostome

The first known use of protostome was in 1959

See more words from the same year

More from Merriam-Webster on protostome

Britannica.com: Encyclopedia article about protostome

Comments on protostome

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

WORD OF THE DAY

to move or proceed with twists and turns

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!