1. 1. The act or process of expanding; dilation.
   2. The condition of being expanded or stretched.
   3. A dilated formation or part.
2. Medicine. The condition of being abnormally enlarged or dilated, as of an organ, orifice, or tubular structure: dilatation of the stomach. Also called dilation.
3. Lengthy explanation or elaboration of a subject in writing or speech.

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.