Merriam-Webster Logo
SINCE 1828
Menu
dictionary thesaurus

Orthoceras

noun
Or·​thoc·​er·​as | \ ȯ(r)ˈthäsərəs\

Definition of Orthoceras

: an ill-defined genus of extinct nautiloid cephalopod mollusks having a long tapering shell that is nearly or quite straight, almost smooth, and many-chambered

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!

History and Etymology for Orthoceras

New Latin, from orth- + -ceras

Keep scrolling for more

Learn More about Orthoceras

Statistics for Orthoceras

Look-up Popularity

Comments on Orthoceras

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

Show Comments  Hide Comments 

WORD OF THE DAY

disparage

Listen to the pronounciation of disparage

to speak slightingly about or to degrade

Get Word of the Day daily email!

Test Your Vocabulary

Challenging Vocabulary Quiz Returns!

  • stylized drawing of woman pole vaulting across gap to get trophy
  • Which is a synonym of fuliginous?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
SCRABBLE® Sprint

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