proostracum

noun

pro·​os·​tra·​cum

prōˈästrə̇kəm

plural proostraca

-kə

: the anterior horny or calcareous prolongation of the phragmocone of belemnites and related cephalopods

Word History

Etymology

New Latin, from pro- entry 1 + Greek ostrakon earthen vessel, potsherd, shell

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!