1. The act of expressing, conveying, or representing in words, art, music, or movement; a manifestation: an expression of rural values.
2. Something that expresses or communicates: Let this plaque serve as an expression of our esteem.
3. Mathematics. A symbol or combination of symbols that represents a quantity or a relationship between quantities.
4. The manner in which one expresses oneself, especially in speaking, depicting, or performing.
5. A particular word or phrase: "an old Yankee expression . . . 'Stand up and be counted'" (Charles Kuralt).
6. The outward manifestation of a mood or a disposition: My tears are an expression of my grief.
7. A facial aspect or a look that conveys a special feeling: an expression of scorn.
8. The act of pressing or squeezing out.
9. Genetics. The act or process of expressing a gene.

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.