1. The process of diffusing or the condition of being diffused.
2. Needless profusion of words; prolixity.
3. Physics.
   1. The scattering of incident light by reflection from a rough surface.
   2. The transmission of light through a translucent material.
   3. The spontaneous intermingling of the particles of two or more substances as a result of random thermal motion.
4. The spread of linguistic or cultural practices or innovations within a community or from one community to another.

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.