Design Glossary...

dummy
A dummy counts as an example of a piece of design work (brochure, ad, book cover etc.) that needs to be approved by the client. Once the client approves the dummy, the designer creates and prints the final design.

leading
The vertical spacing (measured in points) between lines of text.

 clipping path
A function that allows a shape to mask part of an image. The masked part of the image can be edited but won't let you work past the borders of the clipping path.
density
The higher the density of an image, the greater the opacity. The lower the density, the more transparent the image is.
master page
A feature found in page layout software that allows the user to create a consistent page layout. Repeating elements like page numbers are created once on a master. This allows the user to avoid adding the numbers to each page manually.