1. The side or surface that is underneath; the bottom side. Also called undersurface.
2. The side that is less desirable, reputable, or noble than the obverse: "hunger, isolation, filth, the underside of [a] hellish regime" (National Review).

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.