1. A daily record, especially a personal record of events, experiences, and observations; a journal.
2. A book for use in keeping a personal record, as of experiences.

[Latin diārium, daily allowance, daily journal, from diēs, day.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.