1. A word, phrase, or name, usually set in boldface or other distinctive type, that serves as the heading for an entry in a dictionary, encyclopedia, or similar reference work. Also called entry word.
2. Grammar. A word that may be modified by an adjunct.

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.