Just trying to find a definition.
I was asked this in an interview and I assumed it was a polygon created by incorrectly modifying a another polygon in a coverage.
According to my best googling resulting in this code: http://www.falconview.org/svn/FalconView/trunk/public/fvw_core/Utility/GeometryUtils.cpp and my limited understanding of it. A shaved polygon occurs when you eliminate a polygon and your surface no longer forms a convex hull. I would assume this is important in a situation where keeping area constant (such as city limits).