Join Us On

Browse Dictionary Browse Thesaurus

Get our free apps!iPhone•iPad•Android

Medical Dictionary

planum

noun pla·num \ˈplā-nəm\

plural pla·na \-nə\

Medical Definition of PLANUM

: a flat surface of bone especially of the skull

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

Put-downs with flair

How to use a word that (literally) drives some people nuts.

Test your vocab with our fun, fast game

Ailurophobia, and 9 other unusual fears

Join Us

Merriam-Webster
on Facebook

Merriam-Webster
on Twitter

Bookstore: Digital and Print

Merriam-Webster references for Mobile, Kindle, print, and more.

See All

Other Merriam-Webster Dictionaries